diff --git a/ash/display/window_tree_host_manager_unittest.cc b/ash/display/window_tree_host_manager_unittest.cc
index 421a0c68dd4c3c..90725a6113e496 100644
--- a/ash/display/window_tree_host_manager_unittest.cc
+++ b/ash/display/window_tree_host_manager_unittest.cc
@@ -1489,7 +1489,8 @@ class RootWindowTestObserver : public aura::WindowObserver {
 
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override {
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
     shelf_display_bounds_ = ScreenUtil::GetDisplayBoundsWithShelf(window);
   }
 
diff --git a/ash/magnifier/magnification_controller.cc b/ash/magnifier/magnification_controller.cc
index a610020ef9cb75..68ac9e3673c889 100644
--- a/ash/magnifier/magnification_controller.cc
+++ b/ash/magnifier/magnification_controller.cc
@@ -140,7 +140,8 @@ class MagnificationControllerImpl : public MagnificationController,
   void OnWindowDestroying(aura::Window* root_window) override;
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
   // Redraws the magnification window with the given origin position and the
   // given scale. Returns true if the window is changed; otherwise, false.
@@ -566,7 +567,8 @@ void MagnificationControllerImpl::OnWindowDestroying(
 void MagnificationControllerImpl::OnWindowBoundsChanged(
     aura::Window* window,
     const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   // TODO(yoshiki): implement here. crbug.com/230979
 }
 
diff --git a/ash/wallpaper/wallpaper_widget_controller.cc b/ash/wallpaper/wallpaper_widget_controller.cc
index 7a6ad82af472b1..d7f71b086ac9a2 100644
--- a/ash/wallpaper/wallpaper_widget_controller.cc
+++ b/ash/wallpaper/wallpaper_widget_controller.cc
@@ -108,7 +108,8 @@ void WallpaperWidgetController::RemoveObservers() {
 void WallpaperWidgetController::OnWindowBoundsChanged(
     aura::Window* window,
     const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   SetBounds(new_bounds);
 }
 
diff --git a/ash/wallpaper/wallpaper_widget_controller.h b/ash/wallpaper/wallpaper_widget_controller.h
index 0790fd0da39fc6..58df7423664a5d 100644
--- a/ash/wallpaper/wallpaper_widget_controller.h
+++ b/ash/wallpaper/wallpaper_widget_controller.h
@@ -53,7 +53,8 @@ class ASH_EXPORT WallpaperWidgetController : public views::WidgetObserver,
   // aura::WindowObserver:
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
   views::Widget* widget_;
 
diff --git a/ash/wm/lock_layout_manager.cc b/ash/wm/lock_layout_manager.cc
index 21b5f3b8df89f8..60ffb58a188c6d 100644
--- a/ash/wm/lock_layout_manager.cc
+++ b/ash/wm/lock_layout_manager.cc
@@ -77,7 +77,8 @@ void LockLayoutManager::OnWindowDestroying(aura::Window* window) {
 
 void LockLayoutManager::OnWindowBoundsChanged(aura::Window* window,
                                               const gfx::Rect& old_bounds,
-                                              const gfx::Rect& new_bounds) {
+                                              const gfx::Rect& new_bounds,
+                                              ui::PropertyChangeReason reason) {
   if (root_window_ == window) {
     const wm::WMEvent wm_event(wm::WM_EVENT_DISPLAY_BOUNDS_CHANGED);
     AdjustWindowsForWorkAreaChange(&wm_event);
diff --git a/ash/wm/lock_layout_manager.h b/ash/wm/lock_layout_manager.h
index bdaaa5cad9ce9e..32f47961d18d83 100644
--- a/ash/wm/lock_layout_manager.h
+++ b/ash/wm/lock_layout_manager.h
@@ -60,7 +60,8 @@ class ASH_EXPORT LockLayoutManager
   void OnWindowDestroying(aura::Window* window) override;
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
   // ShellObserver:
   void OnVirtualKeyboardStateChanged(bool activated,
diff --git a/ash/wm/overview/window_grid.cc b/ash/wm/overview/window_grid.cc
index 93bc08ee32bff0..d54a5a030f3aef 100644
--- a/ash/wm/overview/window_grid.cc
+++ b/ash/wm/overview/window_grid.cc
@@ -597,7 +597,8 @@ void WindowGrid::OnWindowDestroying(aura::Window* window) {
 
 void WindowGrid::OnWindowBoundsChanged(aura::Window* window,
                                        const gfx::Rect& old_bounds,
-                                       const gfx::Rect& new_bounds) {
+                                       const gfx::Rect& new_bounds,
+                                       ui::PropertyChangeReason reason) {
   // During preparation, window bounds can change. Ignore bounds
   // change notifications in this case; we'll reposition soon.
   if (!prepared_for_overview_)
diff --git a/ash/wm/overview/window_grid.h b/ash/wm/overview/window_grid.h
index 467933d309a8ff..9911b39b81e2f0 100644
--- a/ash/wm/overview/window_grid.h
+++ b/ash/wm/overview/window_grid.h
@@ -140,7 +140,8 @@ class ASH_EXPORT WindowGrid : public aura::WindowObserver,
   // TODO(flackr): Handle window bounds changed in WindowSelectorItem.
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
   // wm::WindowStateObserver:
   void OnPostWindowStateTypeChange(wm::WindowState* window_state,
diff --git a/ash/wm/resize_shadow.cc b/ash/wm/resize_shadow.cc
index d73829e3416537..fae090293ac074 100644
--- a/ash/wm/resize_shadow.cc
+++ b/ash/wm/resize_shadow.cc
@@ -100,7 +100,8 @@ ResizeShadow::~ResizeShadow() {
 
 void ResizeShadow::OnWindowBoundsChanged(aura::Window* window,
                                          const gfx::Rect& old_bounds,
-                                         const gfx::Rect& new_bounds) {
+                                         const gfx::Rect& new_bounds,
+                                         ui::PropertyChangeReason reason) {
   UpdateBoundsAndVisibility();
 }
 
diff --git a/ash/wm/resize_shadow.h b/ash/wm/resize_shadow.h
index 3ebcf46c798a7a..0d73f19e40dbe1 100644
--- a/ash/wm/resize_shadow.h
+++ b/ash/wm/resize_shadow.h
@@ -30,7 +30,8 @@ class ResizeShadow : public aura::WindowObserver {
   // aura::WindowObserver:
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowHierarchyChanged(const HierarchyChangeParams& params) override;
   void OnWindowStackingChanged(aura::Window* window) override;
 
diff --git a/ash/wm/root_window_layout_manager_unittest.cc b/ash/wm/root_window_layout_manager_unittest.cc
index a8e7da7443f65e..62ced3f1516f55 100644
--- a/ash/wm/root_window_layout_manager_unittest.cc
+++ b/ash/wm/root_window_layout_manager_unittest.cc
@@ -18,7 +18,8 @@ class WindowDeleter : public aura::WindowObserver {
   // aura::WindowObserver::
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override {
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
     delete target_;
   }
 
diff --git a/ash/wm/system_wallpaper_controller.cc b/ash/wm/system_wallpaper_controller.cc
index 1e07c2a9789afe..9517c0d8b7c0bc 100644
--- a/ash/wm/system_wallpaper_controller.cc
+++ b/ash/wm/system_wallpaper_controller.cc
@@ -33,7 +33,8 @@ void SystemWallpaperController::SetColor(SkColor color) {
 void SystemWallpaperController::OnWindowBoundsChanged(
     aura::Window* root,
     const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   DCHECK_EQ(root_window_, root);
   layer_->SetBounds(gfx::Rect(root_window_->layer()->bounds().size()));
 }
diff --git a/ash/wm/system_wallpaper_controller.h b/ash/wm/system_wallpaper_controller.h
index b21426279035ac..09d03f705d4011 100644
--- a/ash/wm/system_wallpaper_controller.h
+++ b/ash/wm/system_wallpaper_controller.h
@@ -35,7 +35,8 @@ class SystemWallpaperController : public aura::WindowObserver {
   // aura::WindowObserver overrides:
   void OnWindowBoundsChanged(aura::Window* root,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
  private:
   class HostContentLayerDelegate;
diff --git a/ash/wm/tablet_mode/tablet_mode_window_manager.cc b/ash/wm/tablet_mode/tablet_mode_window_manager.cc
index a10fa110c45b4a..18bd83d85d243f 100644
--- a/ash/wm/tablet_mode/tablet_mode_window_manager.cc
+++ b/ash/wm/tablet_mode/tablet_mode_window_manager.cc
@@ -159,7 +159,8 @@ void TabletModeWindowManager::OnWindowPropertyChanged(aura::Window* window,
 void TabletModeWindowManager::OnWindowBoundsChanged(
     aura::Window* window,
     const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   if (!IsContainerWindow(window))
     return;
   // Reposition all non maximizeable windows.
diff --git a/ash/wm/tablet_mode/tablet_mode_window_manager.h b/ash/wm/tablet_mode/tablet_mode_window_manager.h
index c7c41e91dbd4cb..0bca08829d61dc 100644
--- a/ash/wm/tablet_mode/tablet_mode_window_manager.h
+++ b/ash/wm/tablet_mode/tablet_mode_window_manager.h
@@ -70,7 +70,8 @@ class ASH_EXPORT TabletModeWindowManager
                                intptr_t old) override;
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowVisibilityChanged(aura::Window* window, bool visible) override;
 
   // display::DisplayObserver:
diff --git a/ash/wm/window_dimmer.cc b/ash/wm/window_dimmer.cc
index 13ad065406052d..27e7b6d9f359ad 100644
--- a/ash/wm/window_dimmer.cc
+++ b/ash/wm/window_dimmer.cc
@@ -59,7 +59,8 @@ void WindowDimmer::SetDimOpacity(float target_opacity) {
 
 void WindowDimmer::OnWindowBoundsChanged(aura::Window* window,
                                          const gfx::Rect& old_bounds,
-                                         const gfx::Rect& new_bounds) {
+                                         const gfx::Rect& new_bounds,
+                                         ui::PropertyChangeReason reason) {
   if (window == parent_)
     window_->SetBounds(gfx::Rect(new_bounds.size()));
 }
diff --git a/ash/wm/window_dimmer.h b/ash/wm/window_dimmer.h
index 473e19cb2b4587..be912dcef21d04 100644
--- a/ash/wm/window_dimmer.h
+++ b/ash/wm/window_dimmer.h
@@ -38,7 +38,8 @@ class ASH_EXPORT WindowDimmer : public aura::WindowObserver {
   // aura::WindowObserver:
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowDestroying(aura::Window* window) override;
   void OnWindowHierarchyChanging(const HierarchyChangeParams& params) override;
 
diff --git a/ash/wm/workspace/workspace_layout_manager.cc b/ash/wm/workspace/workspace_layout_manager.cc
index 72904cdd617ad0..5d39628457e5c6 100644
--- a/ash/wm/workspace/workspace_layout_manager.cc
+++ b/ash/wm/workspace/workspace_layout_manager.cc
@@ -238,7 +238,8 @@ void WorkspaceLayoutManager::OnWindowDestroying(aura::Window* window) {
 void WorkspaceLayoutManager::OnWindowBoundsChanged(
     aura::Window* window,
     const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   if (root_window_ == window) {
     const wm::WMEvent wm_event(wm::WM_EVENT_DISPLAY_BOUNDS_CHANGED);
     AdjustAllWindowsBoundsForWorkAreaChange(&wm_event);
diff --git a/ash/wm/workspace/workspace_layout_manager.h b/ash/wm/workspace/workspace_layout_manager.h
index 69f0ebab343bea..840aef9d883ee0 100644
--- a/ash/wm/workspace/workspace_layout_manager.h
+++ b/ash/wm/workspace/workspace_layout_manager.h
@@ -72,7 +72,8 @@ class ASH_EXPORT WorkspaceLayoutManager
   void OnWindowDestroying(aura::Window* window) override;
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
   // wm::ActivationChangeObserver overrides:
   void OnWindowActivating(ActivationReason reason,
diff --git a/chrome/browser/chromeos/lock_screen_apps/first_app_run_toast_manager.cc b/chrome/browser/chromeos/lock_screen_apps/first_app_run_toast_manager.cc
index f482fb6e2c2f95..cd952d2b10b1d9 100644
--- a/chrome/browser/chromeos/lock_screen_apps/first_app_run_toast_manager.cc
+++ b/chrome/browser/chromeos/lock_screen_apps/first_app_run_toast_manager.cc
@@ -104,7 +104,8 @@ void FirstAppRunToastManager::OnAppWindowActivated(
 void FirstAppRunToastManager::OnWindowBoundsChanged(
     aura::Window* window,
     const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   if (toast_widget_ && window == app_window_->GetNativeWindow())
     AdjustToastWidgetBounds();
 }
diff --git a/chrome/browser/chromeos/lock_screen_apps/first_app_run_toast_manager.h b/chrome/browser/chromeos/lock_screen_apps/first_app_run_toast_manager.h
index 5d44145df5dc93..065f09427e79d2 100644
--- a/chrome/browser/chromeos/lock_screen_apps/first_app_run_toast_manager.h
+++ b/chrome/browser/chromeos/lock_screen_apps/first_app_run_toast_manager.h
@@ -51,7 +51,8 @@ class FirstAppRunToastManager : public extensions::AppWindowRegistry::Observer,
   // aura::WindowObserver:
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
   // extensions::AppWindowRegistry::Observer:
   void OnAppWindowActivated(extensions::AppWindow* app_window) override;
diff --git a/chrome/browser/ui/ash/chrome_keyboard_ui.cc b/chrome/browser/ui/ash/chrome_keyboard_ui.cc
index bf5638519806e8..8048ad9926b719 100644
--- a/chrome/browser/ui/ash/chrome_keyboard_ui.cc
+++ b/chrome/browser/ui/ash/chrome_keyboard_ui.cc
@@ -77,7 +77,8 @@ class WindowBoundsChangeObserver : public aura::WindowObserver {
  private:
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override {
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
     ui_->UpdateInsetsForWindow(window);
   }
   void OnWindowDestroyed(aura::Window* window) override {
@@ -396,7 +397,8 @@ void ChromeKeyboardUI::ResetInsets() {
 
 void ChromeKeyboardUI::OnWindowBoundsChanged(aura::Window* window,
                                              const gfx::Rect& old_bounds,
-                                             const gfx::Rect& new_bounds) {
+                                             const gfx::Rect& new_bounds,
+                                             ui::PropertyChangeReason reason) {
   SetShadowAroundKeyboard();
 }
 
diff --git a/chrome/browser/ui/ash/chrome_keyboard_ui.h b/chrome/browser/ui/ash/chrome_keyboard_ui.h
index 2e05e2d11d909d..98bb397f38730a 100644
--- a/chrome/browser/ui/ash/chrome_keyboard_ui.h
+++ b/chrome/browser/ui/ash/chrome_keyboard_ui.h
@@ -79,7 +79,8 @@ class ChromeKeyboardUI : public keyboard::KeyboardUI,
   // aura::WindowObserver overrides:
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowDestroyed(aura::Window* window) override;
   void OnWindowParentChanged(aura::Window* window,
                              aura::Window* parent) override;
diff --git a/chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos_unittest.cc b/chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos_unittest.cc
index 905f21b21242d5..8e61d11ab5a3a6 100644
--- a/chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos_unittest.cc
+++ b/chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos_unittest.cc
@@ -1279,7 +1279,8 @@ class TestWindowObserver : public aura::WindowObserver {
 
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override {
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
     resize_calls_++;
   }
 
diff --git a/components/exo/shell_surface.cc b/components/exo/shell_surface.cc
index 952ba41423f148..b1a4e3552999e1 100644
--- a/components/exo/shell_surface.cc
+++ b/components/exo/shell_surface.cc
@@ -1042,7 +1042,8 @@ void ShellSurface::OnPostWindowStateTypeChange(
 
 void ShellSurface::OnWindowBoundsChanged(aura::Window* window,
                                          const gfx::Rect& old_bounds,
-                                         const gfx::Rect& new_bounds) {
+                                         const gfx::Rect& new_bounds,
+                                         ui::PropertyChangeReason reason) {
   // TODO(domlaskowski): For BoundsMode::CLIENT, the configure callback does not
   // yet support resizing. See crbug.com/699746.
   if (bounds_mode_ == BoundsMode::CLIENT)
diff --git a/components/exo/shell_surface.h b/components/exo/shell_surface.h
index c81eb14dddf77a..5a01e9b5125871 100644
--- a/components/exo/shell_surface.h
+++ b/components/exo/shell_surface.h
@@ -273,7 +273,8 @@ class ShellSurface : public SurfaceTreeHost,
   // Overridden from aura::WindowObserver:
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowDestroying(aura::Window* window) override;
 
   // Overridden from wm::ActivationChangeObserver:
diff --git a/components/ui_devtools/views/window_element.cc b/components/ui_devtools/views/window_element.cc
index 537d022d920cc6..2213ffb445f80a 100644
--- a/components/ui_devtools/views/window_element.cc
+++ b/components/ui_devtools/views/window_element.cc
@@ -58,7 +58,8 @@ void WindowElement::OnWindowStackingChanged(aura::Window* window) {
 
 void WindowElement::OnWindowBoundsChanged(aura::Window* window,
                                           const gfx::Rect& old_bounds,
-                                          const gfx::Rect& new_bounds) {
+                                          const gfx::Rect& new_bounds,
+                                          ui::PropertyChangeReason reason) {
   DCHECK_EQ(window_, window);
   delegate()->OnUIElementBoundsChanged(this);
 }
diff --git a/components/ui_devtools/views/window_element.h b/components/ui_devtools/views/window_element.h
index e2ad70d1846c36..06130ed872c549 100644
--- a/components/ui_devtools/views/window_element.h
+++ b/components/ui_devtools/views/window_element.h
@@ -29,7 +29,8 @@ class WindowElement : public aura::WindowObserver, public UIElement {
   void OnWindowStackingChanged(aura::Window* window) override;
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
   // UIElement:
   std::vector<std::pair<std::string, std::string>> GetCustomAttributes()
diff --git a/content/browser/media/capture/aura_window_capture_machine.cc b/content/browser/media/capture/aura_window_capture_machine.cc
index da9f18dfa6df99..51134be0830996 100644
--- a/content/browser/media/capture/aura_window_capture_machine.cc
+++ b/content/browser/media/capture/aura_window_capture_machine.cc
@@ -407,7 +407,8 @@ void AuraWindowCaptureMachine::CopyOutputFinishedForVideo(
 void AuraWindowCaptureMachine::OnWindowBoundsChanged(
     aura::Window* window,
     const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK(desktop_window_ && window == desktop_window_);
 
diff --git a/content/browser/media/capture/aura_window_capture_machine.h b/content/browser/media/capture/aura_window_capture_machine.h
index e8de893d92e901..d5bcc3faec21bf 100644
--- a/content/browser/media/capture/aura_window_capture_machine.h
+++ b/content/browser/media/capture/aura_window_capture_machine.h
@@ -45,7 +45,8 @@ class AuraWindowCaptureMachine : public media::VideoCaptureMachine,
   // Implements aura::WindowObserver.
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowDestroying(aura::Window* window) override;
   void OnWindowAddedToRootWindow(aura::Window* window) override;
   void OnWindowRemovingFromRootWindow(aura::Window* window,
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index ab38e0f07a7371..72fb290ddd21f0 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -362,7 +362,8 @@ class RenderWidgetHostViewAura::WindowAncestorObserver
 
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override {
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
     DCHECK(ancestors_.find(window) != ancestors_.end());
     if (new_bounds.origin() != old_bounds.origin())
       view_->HandleParentBoundsChanged();
diff --git a/content/browser/web_contents/web_contents_view_aura.cc b/content/browser/web_contents/web_contents_view_aura.cc
index 4f5ed61dd212d5..58a44d530aa6ad 100644
--- a/content/browser/web_contents/web_contents_view_aura.cc
+++ b/content/browser/web_contents/web_contents_view_aura.cc
@@ -449,7 +449,8 @@ class WebContentsViewAura::WindowObserver
 
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override {
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
     if (window == host_window_ || window == view_->window_.get()) {
       SendScreenRects();
       if (old_bounds.origin() != new_bounds.origin()) {
diff --git a/mash/simple_wm/move_loop.cc b/mash/simple_wm/move_loop.cc
index 45d210a19475ef..1336e34d93a43a 100644
--- a/mash/simple_wm/move_loop.cc
+++ b/mash/simple_wm/move_loop.cc
@@ -223,7 +223,8 @@ void MoveLoop::OnWindowHierarchyChanged(const HierarchyChangeParams& params) {
 
 void MoveLoop::OnWindowBoundsChanged(aura::Window* window,
                                      const gfx::Rect& old_bounds,
-                                     const gfx::Rect& new_bounds) {
+                                     const gfx::Rect& new_bounds,
+                                     ui::PropertyChangeReason reason) {
   DCHECK_EQ(window, target_);
   if (!changing_bounds_)
     Cancel();
diff --git a/mash/simple_wm/move_loop.h b/mash/simple_wm/move_loop.h
index 333d043f9142d9..dd115bd916e606 100644
--- a/mash/simple_wm/move_loop.h
+++ b/mash/simple_wm/move_loop.h
@@ -90,7 +90,8 @@ class MoveLoop : public aura::WindowObserver {
   void OnWindowHierarchyChanged(const HierarchyChangeParams& params) override;
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowVisibilityChanged(aura::Window* window, bool visible) override;
 
   // The window this MoveLoop is acting on. |target_| is set to null if the
diff --git a/services/ui/ws/window_manager_client_unittest.cc b/services/ui/ws/window_manager_client_unittest.cc
index aadd8893bfc6ff..599334481f0c05 100644
--- a/services/ui/ws/window_manager_client_unittest.cc
+++ b/services/ui/ws/window_manager_client_unittest.cc
@@ -111,7 +111,8 @@ class BoundsChangeObserver : public aura::WindowObserver {
   // Overridden from WindowObserver:
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override {
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
     DCHECK_EQ(window, window_);
     EXPECT_TRUE(WindowServerTestBase::QuitRunLoop());
   }
diff --git a/ui/app_list/presenter/app_list_presenter_impl.cc b/ui/app_list/presenter/app_list_presenter_impl.cc
index bcfef1192d4f3e..a766319bf805c2 100644
--- a/ui/app_list/presenter/app_list_presenter_impl.cc
+++ b/ui/app_list/presenter/app_list_presenter_impl.cc
@@ -277,9 +277,11 @@ void AppListPresenterImpl::OnWindowFocused(aura::Window* gained_focus,
 
 ////////////////////////////////////////////////////////////////////////////////
 // AppListPresenterImpl,  aura::WindowObserver implementation:
-void AppListPresenterImpl::OnWindowBoundsChanged(aura::Window* root,
-                                                 const gfx::Rect& old_bounds,
-                                                 const gfx::Rect& new_bounds) {
+void AppListPresenterImpl::OnWindowBoundsChanged(
+    aura::Window* root,
+    const gfx::Rect& old_bounds,
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   if (presenter_delegate_)
     presenter_delegate_->UpdateBounds();
 }
diff --git a/ui/app_list/presenter/app_list_presenter_impl.h b/ui/app_list/presenter/app_list_presenter_impl.h
index 4cb66df78d7c96..18da63b5695207 100644
--- a/ui/app_list/presenter/app_list_presenter_impl.h
+++ b/ui/app_list/presenter/app_list_presenter_impl.h
@@ -109,7 +109,8 @@ class APP_LIST_PRESENTER_EXPORT AppListPresenterImpl
   // aura::WindowObserver overrides:
   void OnWindowBoundsChanged(aura::Window* root,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
   // ui::ImplicitAnimationObserver overrides:
   void OnImplicitAnimationsCompleted() override;
diff --git a/ui/arc/notification/arc_notification_content_view.cc b/ui/arc/notification/arc_notification_content_view.cc
index 6e5f3077108a86..b34d56d5ed3089 100644
--- a/ui/arc/notification/arc_notification_content_view.cc
+++ b/ui/arc/notification/arc_notification_content_view.cc
@@ -679,7 +679,8 @@ void ArcNotificationContentView::GetAccessibleNodeData(
 void ArcNotificationContentView::OnWindowBoundsChanged(
     aura::Window* window,
     const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   if (in_layout_)
     return;
 
diff --git a/ui/arc/notification/arc_notification_content_view.h b/ui/arc/notification/arc_notification_content_view.h
index 545ed173f81e63..2178286451867b 100644
--- a/ui/arc/notification/arc_notification_content_view.h
+++ b/ui/arc/notification/arc_notification_content_view.h
@@ -89,7 +89,8 @@ class ArcNotificationContentView
   // aura::WindowObserver
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowDestroying(aura::Window* window) override;
 
   // ArcNotificationItem::Observer
diff --git a/ui/aura/test/test_screen.cc b/ui/aura/test/test_screen.cc
index 2f16addd50434d..d7796a672a5835 100644
--- a/ui/aura/test/test_screen.cc
+++ b/ui/aura/test/test_screen.cc
@@ -134,8 +134,10 @@ gfx::Transform TestScreen::GetUIScaleTransform() const {
   return ui_scale;
 }
 
-void TestScreen::OnWindowBoundsChanged(
-    Window* window, const gfx::Rect& old_bounds, const gfx::Rect& new_bounds) {
+void TestScreen::OnWindowBoundsChanged(Window* window,
+                                       const gfx::Rect& old_bounds,
+                                       const gfx::Rect& new_bounds,
+                                       ui::PropertyChangeReason reason) {
   DCHECK_EQ(host_->window(), window);
   display::Display display(GetPrimaryDisplay());
   display.SetSize(gfx::ScaleToFlooredSize(new_bounds.size(),
diff --git a/ui/aura/test/test_screen.h b/ui/aura/test/test_screen.h
index 7f625d3b5d629d..abee5232168a5a 100644
--- a/ui/aura/test/test_screen.h
+++ b/ui/aura/test/test_screen.h
@@ -48,7 +48,8 @@ class TestScreen : public display::ScreenBase, public WindowObserver {
   // WindowObserver overrides:
   void OnWindowBoundsChanged(Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowDestroying(Window* window) override;
 
   // display::Screen overrides:
diff --git a/ui/aura/window.cc b/ui/aura/window.cc
index bc8c9b43cca10f..144c13d81821c4 100644
--- a/ui/aura/window.cc
+++ b/ui/aura/window.cc
@@ -1070,12 +1070,12 @@ void Window::OnLayerBoundsChanged(const gfx::Rect& old_bounds,
   if (delegate_)
     delegate_->OnBoundsChanged(old_bounds, bounds_);
   for (auto& observer : observers_)
-    observer.OnWindowBoundsChanged(this, old_bounds, bounds_);
+    observer.OnWindowBoundsChanged(this, old_bounds, bounds_, reason);
 }
 
 void Window::OnLayerOpacityChanged(ui::PropertyChangeReason reason) {
   for (WindowObserver& observer : observers_)
-    observer.OnWindowOpacityChanged(this);
+    observer.OnWindowOpacityChanged(this, reason);
 }
 
 bool Window::CanAcceptEvent(const ui::Event& event) {
diff --git a/ui/aura/window_event_dispatcher.cc b/ui/aura/window_event_dispatcher.cc
index 6a673a4fcdd060..a923a15fee8fbe 100644
--- a/ui/aura/window_event_dispatcher.cc
+++ b/ui/aura/window_event_dispatcher.cc
@@ -698,9 +698,11 @@ void WindowEventDispatcher::OnWindowVisibilityChanged(Window* window,
     OnWindowHidden(window, WINDOW_HIDDEN);
 }
 
-void WindowEventDispatcher::OnWindowBoundsChanged(Window* window,
-                                                  const gfx::Rect& old_bounds,
-                                                  const gfx::Rect& new_bounds) {
+void WindowEventDispatcher::OnWindowBoundsChanged(
+    Window* window,
+    const gfx::Rect& old_bounds,
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   if (!host_->window()->Contains(window))
     return;
 
diff --git a/ui/aura/window_event_dispatcher.h b/ui/aura/window_event_dispatcher.h
index 946d0b8150d11a..0ddf99f0076457 100644
--- a/ui/aura/window_event_dispatcher.h
+++ b/ui/aura/window_event_dispatcher.h
@@ -213,7 +213,8 @@ class AURA_EXPORT WindowEventDispatcher : public ui::EventProcessor,
   void OnWindowVisibilityChanged(Window* window, bool visible) override;
   void OnWindowBoundsChanged(Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowTransforming(Window* window) override;
   void OnWindowTransformed(Window* window) override;
 
diff --git a/ui/aura/window_observer.h b/ui/aura/window_observer.h
index 1ed168de7f1d09..d1cf751cde1554 100644
--- a/ui/aura/window_observer.h
+++ b/ui/aura/window_observer.h
@@ -8,6 +8,7 @@
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "ui/aura/aura_export.h"
+#include "ui/compositor/property_change_reason.h"
 
 namespace gfx {
 class Rect;
@@ -78,15 +79,26 @@ class AURA_EXPORT WindowObserver {
   // on.
   virtual void OnWindowVisibilityChanged(Window* window, bool visible) {}
 
-  // Invoked when SetBounds() is invoked on |window|. |old_bounds| and
-  // |new_bounds| are in parent coordinates.
+  // Invoked when the bounds of the |window|'s layer are set. |old_bounds| and
+  // |new_bounds| are in parent coordinates. |reason| indicates whether the
+  // bounds were set directly or by an animation. This will be called at every
+  // step of a bounds animation. The client can determine whether the animation
+  // is ending by calling window->layer()->GetAnimator()->IsAnimatingProperty(
+  // ui::LayerAnimationElement::BOUNDS).
   virtual void OnWindowBoundsChanged(Window* window,
                                      const gfx::Rect& old_bounds,
-                                     const gfx::Rect& new_bounds) {}
-
-  // Invoked when the opacity of the |window|'s layer changes. Can be invoked
-  // multiple times during animation.
-  virtual void OnWindowOpacityChanged(Window* window) {}
+                                     const gfx::Rect& new_bounds,
+                                     ui::PropertyChangeReason reason) {}
+
+  // Invoked when the opacity of the |window|'s layer is set. |reason| indicates
+  // whether the opacity was set directly or by an animation. This won't
+  // necessarily be called at every step of an animation. However, it will
+  // always be called before the first frame of the animation is rendered and
+  // when the animation ends. The client can determine whether the animation is
+  // ending by calling window->layer()->GetAnimator()->IsAnimatingProperty(
+  // ui::LayerAnimationElement::OPACITY).
+  virtual void OnWindowOpacityChanged(Window* window,
+                                      ui::PropertyChangeReason reason) {}
 
   // Invoked when SetTransform() is invoked on |window|.
   virtual void OnWindowTransforming(Window* window) {}
diff --git a/ui/aura/window_unittest.cc b/ui/aura/window_unittest.cc
index 28286b9a755fbe..ef7d5cc169debc 100644
--- a/ui/aura/window_unittest.cc
+++ b/ui/aura/window_unittest.cc
@@ -1747,9 +1747,20 @@ class WindowObserverTest : public WindowTest,
     int changed_count;
   };
 
+  struct WindowBoundsInfo {
+    int changed_count = 0;
+    Window* window = nullptr;
+    gfx::Rect old_bounds;
+    gfx::Rect new_bounds;
+    ui::PropertyChangeReason reason =
+        ui::PropertyChangeReason::NOT_FROM_ANIMATION;
+  };
+
   struct WindowOpacityInfo {
     int changed_count = 0;
     Window* window = nullptr;
+    ui::PropertyChangeReason reason =
+        ui::PropertyChangeReason::NOT_FROM_ANIMATION;
   };
 
   WindowObserverTest()
@@ -1765,6 +1776,10 @@ class WindowObserverTest : public WindowTest,
     return visibility_info_.get();
   }
 
+  const WindowBoundsInfo& window_bounds_info() const {
+    return window_bounds_info_;
+  }
+
   const WindowOpacityInfo& window_opacity_info() const {
     return window_opacity_info_;
   }
@@ -1823,9 +1838,22 @@ class WindowObserverTest : public WindowTest,
     old_property_value_ = old;
   }
 
-  void OnWindowOpacityChanged(Window* window) override {
+  void OnWindowBoundsChanged(Window* window,
+                             const gfx::Rect& old_bounds,
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
+    ++window_bounds_info_.changed_count;
+    window_bounds_info_.window = window;
+    window_bounds_info_.old_bounds = old_bounds;
+    window_bounds_info_.new_bounds = new_bounds;
+    window_bounds_info_.reason = reason;
+  }
+
+  void OnWindowOpacityChanged(Window* window,
+                              ui::PropertyChangeReason reason) override {
     ++window_opacity_info_.changed_count;
     window_opacity_info_.window = window;
+    window_opacity_info_.reason = reason;
   }
 
   int added_count_;
@@ -1835,6 +1863,7 @@ class WindowObserverTest : public WindowTest,
   const void* property_key_;
   intptr_t old_property_value_;
   std::vector<std::pair<int, int> > transform_notifications_;
+  WindowBoundsInfo window_bounds_info_;
   WindowOpacityInfo window_opacity_info_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowObserverTest);
@@ -1963,14 +1992,91 @@ TEST_P(WindowObserverTest, PropertyChanged) {
       reinterpret_cast<const void*>(NULL), -3), PropertyChangeInfoAndClear());
 }
 
+// Verify that WindowObserver::OnWindowBoundsChanged() is notified when the
+// bounds of a Window's Layer change without an animation.
+TEST_P(WindowObserverTest, WindowBoundsChanged) {
+  std::unique_ptr<Window> window(CreateTestWindowWithId(1, root_window()));
+  window->AddObserver(this);
+  const gfx::Rect initial_bounds = window->bounds();
+  constexpr gfx::Rect kTargetBounds(10, 20, 30, 40);
+  window->layer()->SetBounds(kTargetBounds);
+  ASSERT_EQ(1, window_bounds_info().changed_count);
+  EXPECT_EQ(window.get(), window_bounds_info().window);
+  EXPECT_EQ(initial_bounds, window_bounds_info().old_bounds);
+  EXPECT_EQ(kTargetBounds, window_bounds_info().new_bounds);
+  EXPECT_EQ(ui::PropertyChangeReason::NOT_FROM_ANIMATION,
+            window_bounds_info().reason);
+}
+
+// Verify that WindowObserver::OnWindowBoundsChanged() is notified at every step
+// of a bounds animation.
+TEST_P(WindowObserverTest, WindowBoundsChangedAnimation) {
+  std::unique_ptr<Window> window(CreateTestWindowWithId(1, root_window()));
+  window->AddObserver(this);
+  const gfx::Rect initial_bounds = window->bounds();
+  constexpr gfx::Rect kTargetBounds(10, 20, 30, 40);
+  const gfx::Rect step_bounds =
+      gfx::Tween::RectValueBetween(0.5, initial_bounds, kTargetBounds);
+
+  ui::ScopedAnimationDurationScaleMode scoped_animation_duration_scale_mode(
+      ui::ScopedAnimationDurationScaleMode::NORMAL_DURATION);
+  ui::ScopedLayerAnimationSettings settings(window->layer()->GetAnimator());
+  window->layer()->SetBounds(kTargetBounds);
+  ASSERT_EQ(0, window_opacity_info().changed_count);
+
+  window->layer()->GetAnimator()->Step(
+      window->layer()->GetAnimator()->last_step_time() +
+      settings.GetTransitionDuration() / 2);
+  ASSERT_EQ(1, window_bounds_info().changed_count);
+  EXPECT_EQ(window.get(), window_bounds_info().window);
+  EXPECT_EQ(initial_bounds, window_bounds_info().old_bounds);
+  EXPECT_EQ(step_bounds, window_bounds_info().new_bounds);
+  EXPECT_EQ(ui::PropertyChangeReason::FROM_ANIMATION,
+            window_bounds_info().reason);
+
+  window->layer()->GetAnimator()->StopAnimatingProperty(
+      ui::LayerAnimationElement::BOUNDS);
+  ASSERT_EQ(2, window_bounds_info().changed_count);
+  EXPECT_EQ(window.get(), window_bounds_info().window);
+  EXPECT_EQ(step_bounds, window_bounds_info().old_bounds);
+  EXPECT_EQ(kTargetBounds, window_bounds_info().new_bounds);
+  EXPECT_EQ(ui::PropertyChangeReason::FROM_ANIMATION,
+            window_bounds_info().reason);
+}
+
 // Verify that WindowObserver::OnWindowOpacityChanged() is notified when the
-// opacity of a Window's Layer changes.
+// opacity of a Window's Layer changes without an animation.
 TEST_P(WindowObserverTest, WindowOpacityChanged) {
   std::unique_ptr<Window> window(CreateTestWindowWithId(1, root_window()));
   window->AddObserver(this);
   window->layer()->SetOpacity(0.5f);
   ASSERT_EQ(1, window_opacity_info().changed_count);
   EXPECT_EQ(window.get(), window_opacity_info().window);
+  EXPECT_EQ(ui::PropertyChangeReason::NOT_FROM_ANIMATION,
+            window_opacity_info().reason);
+}
+
+// Verify that WindowObserver::OnWindowOpacityChanged() is notified at the
+// beginning and at the end of a threaded opacity animation.
+TEST_P(WindowObserverTest, WindowOpacityChangedAnimation) {
+  std::unique_ptr<Window> window(CreateTestWindowWithId(1, root_window()));
+  window->AddObserver(this);
+
+  ui::ScopedAnimationDurationScaleMode scoped_animation_duration_scale_mode(
+      ui::ScopedAnimationDurationScaleMode::NORMAL_DURATION);
+  ui::ScopedLayerAnimationSettings settings(window->layer()->GetAnimator());
+  window->layer()->SetOpacity(0.5f);
+  ASSERT_EQ(1, window_opacity_info().changed_count);
+  EXPECT_EQ(window.get(), window_opacity_info().window);
+  EXPECT_EQ(ui::PropertyChangeReason::FROM_ANIMATION,
+            window_opacity_info().reason);
+
+  window->layer()->GetAnimator()->StopAnimatingProperty(
+      ui::LayerAnimationElement::OPACITY);
+  ASSERT_EQ(2, window_opacity_info().changed_count);
+  EXPECT_EQ(window.get(), window_opacity_info().window);
+  EXPECT_EQ(ui::PropertyChangeReason::FROM_ANIMATION,
+            window_opacity_info().reason);
 }
 
 TEST_P(WindowTest, AcquireLayer) {
@@ -2339,7 +2445,8 @@ class BoundsChangedWindowObserver : public WindowObserver {
 
   void OnWindowBoundsChanged(Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override {
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
     root_set_ = window->GetRootWindow() != NULL;
   }
 
diff --git a/ui/keyboard/keyboard_controller.cc b/ui/keyboard/keyboard_controller.cc
index 08af41fd157852..71497dd4c3d0eb 100644
--- a/ui/keyboard/keyboard_controller.cc
+++ b/ui/keyboard/keyboard_controller.cc
@@ -435,9 +435,11 @@ void KeyboardController::OnWindowRemovingFromRootWindow(aura::Window* window,
     window->GetRootWindow()->RemoveObserver(this);
 }
 
-void KeyboardController::OnWindowBoundsChanged(aura::Window* window,
-                                               const gfx::Rect& old_bounds,
-                                               const gfx::Rect& new_bounds) {
+void KeyboardController::OnWindowBoundsChanged(
+    aura::Window* window,
+    const gfx::Rect& old_bounds,
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   if (!window->IsRootWindow())
     return;
   // Keep the same height when window resizes. It gets called when the screen
diff --git a/ui/keyboard/keyboard_controller.h b/ui/keyboard/keyboard_controller.h
index f873899bebb17a..33d2afcc9a39d0 100644
--- a/ui/keyboard/keyboard_controller.h
+++ b/ui/keyboard/keyboard_controller.h
@@ -180,7 +180,8 @@ class KEYBOARD_EXPORT KeyboardController : public ui::InputMethodObserver,
                                       aura::Window* new_root) override;
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
   // InputMethodObserver overrides
   void OnBlur() override {}
diff --git a/ui/views/accessibility/ax_window_obj_wrapper.cc b/ui/views/accessibility/ax_window_obj_wrapper.cc
index 3dbef4ad48f831..0740078fcb6217 100644
--- a/ui/views/accessibility/ax_window_obj_wrapper.cc
+++ b/ui/views/accessibility/ax_window_obj_wrapper.cc
@@ -112,9 +112,11 @@ void AXWindowObjWrapper::OnWindowHierarchyChanged(
     AXAuraObjCache::GetInstance()->Remove(params.target, params.old_parent);
 }
 
-void AXWindowObjWrapper::OnWindowBoundsChanged(aura::Window* window,
-                                               const gfx::Rect& old_bounds,
-                                               const gfx::Rect& new_bounds) {
+void AXWindowObjWrapper::OnWindowBoundsChanged(
+    aura::Window* window,
+    const gfx::Rect& old_bounds,
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   if (window != window_)
     return;
 
diff --git a/ui/views/accessibility/ax_window_obj_wrapper.h b/ui/views/accessibility/ax_window_obj_wrapper.h
index 49d82f1de5ec0d..5707a4348e9109 100644
--- a/ui/views/accessibility/ax_window_obj_wrapper.h
+++ b/ui/views/accessibility/ax_window_obj_wrapper.h
@@ -42,7 +42,8 @@ class AXWindowObjWrapper : public AXAuraObjWrapper,
   void OnWindowHierarchyChanged(const HierarchyChangeParams& params) override;
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowPropertyChanged(aura::Window* window,
                                const void* key,
                                intptr_t old) override;
diff --git a/ui/views/controls/menu/display_change_listener_aura.cc b/ui/views/controls/menu/display_change_listener_aura.cc
index 1872281cd97939..724bada87402cc 100644
--- a/ui/views/controls/menu/display_change_listener_aura.cc
+++ b/ui/views/controls/menu/display_change_listener_aura.cc
@@ -23,7 +23,8 @@ class AuraDisplayChangeListener
   // aura::WindowObserver overrides:
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowDestroying(aura::Window* window) override;
 
  private:
@@ -49,7 +50,8 @@ AuraDisplayChangeListener::~AuraDisplayChangeListener() {
 void AuraDisplayChangeListener::OnWindowBoundsChanged(
     aura::Window* window,
     const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   menu_runner_->Cancel();
 }
 
diff --git a/ui/views/controls/native/native_view_host_aura.cc b/ui/views/controls/native/native_view_host_aura.cc
index b25160cf536d02..6dd9aee9c0edd4 100644
--- a/ui/views/controls/native/native_view_host_aura.cc
+++ b/ui/views/controls/native/native_view_host_aura.cc
@@ -224,9 +224,11 @@ gfx::NativeCursor NativeViewHostAura::GetCursor(int x, int y) {
   return gfx::kNullCursor;
 }
 
-void NativeViewHostAura::OnWindowBoundsChanged(aura::Window* window,
-                                               const gfx::Rect& old_bounds,
-                                               const gfx::Rect& new_bounds) {
+void NativeViewHostAura::OnWindowBoundsChanged(
+    aura::Window* window,
+    const gfx::Rect& old_bounds,
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   if (mask_)
     mask_->layer()->SetBounds(gfx::Rect(host_->native_view()->bounds().size()));
 }
diff --git a/ui/views/controls/native/native_view_host_aura.h b/ui/views/controls/native/native_view_host_aura.h
index 87e5c3710f703e..41a56cc63e4e22 100644
--- a/ui/views/controls/native/native_view_host_aura.h
+++ b/ui/views/controls/native/native_view_host_aura.h
@@ -50,7 +50,8 @@ class NativeViewHostAura : public NativeViewHostWrapper,
   void OnWindowDestroyed(aura::Window* window) override;
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
 
   // Reparents the native view with the clipping window existing between it and
   // its old parent, so that the fast resize path works.
diff --git a/ui/views/controls/native/native_view_host_aura_unittest.cc b/ui/views/controls/native/native_view_host_aura_unittest.cc
index 7399c849dd02ec..349d1a1b8c5363 100644
--- a/ui/views/controls/native/native_view_host_aura_unittest.cc
+++ b/ui/views/controls/native/native_view_host_aura_unittest.cc
@@ -63,7 +63,8 @@ class NativeViewHostWindowObserver : public aura::WindowObserver {
 
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override {
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
     EventDetails event;
     event.type = EVENT_BOUNDS_CHANGED;
     event.window = window;
diff --git a/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc b/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
index fbbafceab1cc17..d02c4f4929d11d 100644
--- a/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
+++ b/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
@@ -147,7 +147,8 @@ class DesktopNativeWidgetTopLevelHandler : public aura::WindowObserver {
 
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override {
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override {
     // The position of the window may have changed. Hence we use SetBounds in
     // place of SetSize. We need to pass the bounds in screen coordinates to
     // the Widget::SetBounds function.
diff --git a/ui/wm/core/shadow_controller.cc b/ui/wm/core/shadow_controller.cc
index 31a4abe0ec7544..73dabab6cfe601 100644
--- a/ui/wm/core/shadow_controller.cc
+++ b/ui/wm/core/shadow_controller.cc
@@ -110,7 +110,8 @@ class ShadowController::Impl :
                                intptr_t old) override;
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
+                             const gfx::Rect& new_bounds,
+                             ui::PropertyChangeReason reason) override;
   void OnWindowDestroyed(aura::Window* window) override;
 
  private:
@@ -184,7 +185,8 @@ void ShadowController::Impl::OnWindowPropertyChanged(aura::Window* window,
 void ShadowController::Impl::OnWindowBoundsChanged(
     aura::Window* window,
     const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
+    const gfx::Rect& new_bounds,
+    ui::PropertyChangeReason reason) {
   Shadow* shadow = GetShadowForWindow(window);
   if (shadow)
     shadow->SetContentBounds(gfx::Rect(new_bounds.size()));