diff --git a/ash/display/display_manager.cc b/ash/display/display_manager.cc
index 980a38524f5fa0..e9f0353c309d13 100644
--- a/ash/display/display_manager.cc
+++ b/ash/display/display_manager.cc
@@ -740,23 +740,18 @@ void DisplayManager::ToggleDisplayScaleFactor() {
   UpdateDisplays(new_display_info_list);
 }
 
-void DisplayManager::OnRootWindowResized(const aura::RootWindow* root,
-                                         const gfx::Size& old_size) {
+void DisplayManager::OnRootWindowHostResized(const aura::RootWindow* root) {
   if (change_display_upon_host_resize_) {
     gfx::Display& display = FindDisplayForRootWindow(root);
     gfx::Size old_display_size_in_pixel = display.GetSizeInPixel();
     display_info_[display.id()].SetBounds(
         gfx::Rect(root->GetHostOrigin(), root->GetHostSize()));
-    const gfx::Size& new_root_size = root->bounds().size();
     // It's tricky to support resizing mirror window on desktop.
     if (software_mirroring_enabled_ && mirrored_display_.id() == display.id())
       return;
-    if (old_size != new_root_size) {
-      display.SetSize(display_info_[display.id()].size_in_pixel());
-      Shell::GetInstance()->screen()->NotifyBoundsChanged(display);
-      Shell::GetInstance()->mirror_window_controller()->
-          UpdateWindow();
-    }
+    display.SetSize(display_info_[display.id()].size_in_pixel());
+    Shell::GetInstance()->screen()->NotifyBoundsChanged(display);
+    Shell::GetInstance()->mirror_window_controller()->UpdateWindow();
   }
 }
 
diff --git a/ash/display/display_manager.h b/ash/display/display_manager.h
index 5591b5c0a0a628..f1e52f96783627 100644
--- a/ash/display/display_manager.h
+++ b/ash/display/display_manager.h
@@ -178,8 +178,7 @@ class ASH_EXPORT DisplayManager :
   void ToggleDisplayScaleFactor();
 
   // RootWindowObserver overrides:
-  virtual void OnRootWindowResized(const aura::RootWindow* root,
-                                   const gfx::Size& new_size) OVERRIDE;
+  virtual void OnRootWindowHostResized(const aura::RootWindow* root) OVERRIDE;
 
   // SoftwareMirroringController override:
 #if defined(OS_CHROMEOS)
diff --git a/ash/display/mirror_window_controller.cc b/ash/display/mirror_window_controller.cc
index 739bac0aca627d..885691ef7c1c91 100644
--- a/ash/display/mirror_window_controller.cc
+++ b/ash/display/mirror_window_controller.cc
@@ -224,8 +224,6 @@ void MirrorWindowController::Close() {
   if (root_window_.get()) {
     ui::ContextFactory::GetInstance()->RemoveReflector(reflector_);
     reflector_ = NULL;
-    root_window_->RemoveRootWindowObserver(
-        Shell::GetInstance()->display_manager());
     NoneCaptureClient* capture_client = static_cast<NoneCaptureClient*>(
         aura::client::GetCaptureClient(root_window_.get()));
     delete capture_client;
@@ -279,9 +277,8 @@ void MirrorWindowController::SetMirroredCursorVisibility(bool visible) {
     visible ? cursor_window_->Show() : cursor_window_->Hide();
 }
 
-void MirrorWindowController::OnRootWindowResized(
-    const aura::RootWindow* root,
-    const gfx::Size& old_size) {
+void MirrorWindowController::OnRootWindowHostResized(
+    const aura::RootWindow* root) {
   // Do not use |old_size| as it contains RootWindow's (but not host's) size,
   // and this parameter wil be removed soon.
   if (mirror_window_host_size_ == root->GetHostSize())
diff --git a/ash/display/mirror_window_controller.h b/ash/display/mirror_window_controller.h
index 76a8cfbd7521e2..b9e2e06894c984 100644
--- a/ash/display/mirror_window_controller.h
+++ b/ash/display/mirror_window_controller.h
@@ -58,8 +58,7 @@ class MirrorWindowController : public aura::RootWindowObserver {
   void SetMirroredCursorVisibility(bool visible);
 
   // aura::RootWindowObserver overrides:
-  virtual void OnRootWindowResized(const aura::RootWindow* root,
-                                   const gfx::Size& old_size) OVERRIDE;
+  virtual void OnRootWindowHostResized(const aura::RootWindow* root) OVERRIDE;
 
  private:
   friend class test::MirrorWindowTestApi;
diff --git a/ash/wm/app_list_controller.cc b/ash/wm/app_list_controller.cc
index 02afc69c7bb159..d9bf234e3052bb 100644
--- a/ash/wm/app_list_controller.cc
+++ b/ash/wm/app_list_controller.cc
@@ -157,7 +157,7 @@ void AppListController::SetView(app_list::AppListView* view) {
   widget->AddObserver(this);
   Shell::GetInstance()->AddPreTargetHandler(this);
   Launcher::ForWindow(widget->GetNativeWindow())->AddIconObserver(this);
-  widget->GetNativeView()->GetRootWindow()->AddRootWindowObserver(this);
+  widget->GetNativeView()->GetRootWindow()->AddObserver(this);
   aura::client::GetFocusClient(widget->GetNativeView())->AddObserver(this);
 
   view_->ShowWhenReady();
@@ -172,7 +172,7 @@ void AppListController::ResetView() {
   GetLayer(widget)->GetAnimator()->RemoveObserver(this);
   Shell::GetInstance()->RemovePreTargetHandler(this);
   Launcher::ForWindow(widget->GetNativeWindow())->RemoveIconObserver(this);
-  widget->GetNativeView()->GetRootWindow()->RemoveRootWindowObserver(this);
+  widget->GetNativeView()->GetRootWindow()->RemoveObserver(this);
   aura::client::GetFocusClient(widget->GetNativeView())->RemoveObserver(this);
   view_ = NULL;
 }
@@ -264,9 +264,10 @@ void AppListController::OnWindowFocused(aura::Window* gained_focus,
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-// AppListController,  aura::RootWindowObserver implementation:
-void AppListController::OnRootWindowResized(const aura::RootWindow* root,
-                                            const gfx::Size& old_size) {
+// AppListController,  aura::WindowObserver implementation:
+void AppListController::OnWindowBoundsChanged(aura::Window* root,
+                                              const gfx::Rect& old_bounds,
+                                              const gfx::Rect& new_bounds) {
   UpdateBounds();
 }
 
diff --git a/ash/wm/app_list_controller.h b/ash/wm/app_list_controller.h
index 6f05d6a97dd784..ac163aa9ac8be4 100644
--- a/ash/wm/app_list_controller.h
+++ b/ash/wm/app_list_controller.h
@@ -12,7 +12,7 @@
 #include "base/timer.h"
 #include "ui/app_list/pagination_model_observer.h"
 #include "ui/aura/client/focus_change_observer.h"
-#include "ui/aura/root_window_observer.h"
+#include "ui/aura/window_observer.h"
 #include "ui/base/events/event_handler.h"
 #include "ui/compositor/layer_animation_observer.h"
 #include "ui/gfx/rect.h"
@@ -37,7 +37,7 @@ namespace internal {
 // activation state and desktop mouse click to auto dismiss the UI.
 class AppListController : public ui::EventHandler,
                           public aura::client::FocusChangeObserver,
-                          public aura::RootWindowObserver,
+                          public aura::WindowObserver,
                           public ui::ImplicitAnimationObserver,
                           public views::WidgetObserver,
                           public ShellObserver,
@@ -90,9 +90,10 @@ class AppListController : public ui::EventHandler,
   virtual void OnWindowFocused(aura::Window* gained_focus,
                                aura::Window* lost_focus) OVERRIDE;
 
-  // aura::RootWindowObserver overrides:
-  virtual void OnRootWindowResized(const aura::RootWindow* root,
-                                   const gfx::Size& old_size) OVERRIDE;
+  // aura::WindowObserver overrides:
+  virtual void OnWindowBoundsChanged(aura::Window* root,
+                                     const gfx::Rect& old_bounds,
+                                     const gfx::Rect& new_bounds) OVERRIDE;
 
   // ui::ImplicitAnimationObserver overrides:
   virtual void OnImplicitAnimationsCompleted() OVERRIDE;
diff --git a/ash/wm/base_layout_manager.cc b/ash/wm/base_layout_manager.cc
index 89e99d9371250e..e8146e6d1081b0 100644
--- a/ash/wm/base_layout_manager.cc
+++ b/ash/wm/base_layout_manager.cc
@@ -31,15 +31,12 @@ BaseLayoutManager::BaseLayoutManager(aura::RootWindow* root_window)
     : root_window_(root_window) {
   Shell::GetInstance()->activation_client()->AddObserver(this);
   Shell::GetInstance()->AddShellObserver(this);
-  root_window_->AddRootWindowObserver(this);
   root_window_->AddObserver(this);
 }
 
 BaseLayoutManager::~BaseLayoutManager() {
-  if (root_window_) {
+  if (root_window_)
     root_window_->RemoveObserver(this);
-    root_window_->RemoveRootWindowObserver(this);
-  }
   for (WindowSet::const_iterator i = windows_.begin(); i != windows_.end(); ++i)
     (*i)->RemoveObserver(this);
   Shell::GetInstance()->RemoveShellObserver(this);
@@ -105,14 +102,6 @@ void BaseLayoutManager::SetChildBounds(aura::Window* child,
   SetChildBoundsDirect(child, child_bounds);
 }
 
-/////////////////////////////////////////////////////////////////////////////
-// BaseLayoutManager, RootWindowObserver overrides:
-
-void BaseLayoutManager::OnRootWindowResized(const aura::RootWindow* root,
-                                            const gfx::Size& old_size) {
-  AdjustWindowSizesForScreenChange();
-}
-
 /////////////////////////////////////////////////////////////////////////////
 // BaseLayoutManager, ash::ShellObserver overrides:
 
@@ -150,6 +139,13 @@ void BaseLayoutManager::OnWindowDestroying(aura::Window* window) {
   }
 }
 
+void BaseLayoutManager::OnWindowBoundsChanged(aura::Window* window,
+                                              const gfx::Rect& old_bounds,
+                                              const gfx::Rect& new_bounds) {
+  if (root_window_ == window)
+    AdjustWindowSizesForScreenChange();
+}
+
 //////////////////////////////////////////////////////////////////////////////
 // BaseLayoutManager, aura::client::ActivationChangeObserver implementation:
 
diff --git a/ash/wm/base_layout_manager.h b/ash/wm/base_layout_manager.h
index 7ed9da663a13b0..898bfe90420581 100644
--- a/ash/wm/base_layout_manager.h
+++ b/ash/wm/base_layout_manager.h
@@ -13,7 +13,6 @@
 #include "base/compiler_specific.h"
 #include "ui/aura/client/activation_change_observer.h"
 #include "ui/aura/layout_manager.h"
-#include "ui/aura/root_window_observer.h"
 #include "ui/aura/window_observer.h"
 #include "ui/base/events/event_handler.h"
 #include "ui/base/ui_base_types.h"
@@ -33,7 +32,6 @@ namespace internal {
 // properly.
 class ASH_EXPORT BaseLayoutManager
     : public aura::LayoutManager,
-      public aura::RootWindowObserver,
       public ash::ShellObserver,
       public aura::WindowObserver,
       public aura::client::ActivationChangeObserver {
@@ -61,10 +59,6 @@ class ASH_EXPORT BaseLayoutManager
   virtual void SetChildBounds(aura::Window* child,
                               const gfx::Rect& requested_bounds) OVERRIDE;
 
-  // RootWindowObserver overrides:
-  virtual void OnRootWindowResized(const aura::RootWindow* root,
-                                   const gfx::Size& old_size) OVERRIDE;
-
   // ash::ShellObserver overrides:
   virtual void OnDisplayWorkAreaInsetsChanged() OVERRIDE;
 
@@ -73,6 +67,9 @@ class ASH_EXPORT BaseLayoutManager
                                        const void* key,
                                        intptr_t old) OVERRIDE;
   virtual void OnWindowDestroying(aura::Window* window) OVERRIDE;
+  virtual void OnWindowBoundsChanged(aura::Window* window,
+                                     const gfx::Rect& old_bounds,
+                                     const gfx::Rect& new_bounds) OVERRIDE;
 
   // aura::client::ActivationChangeObserver overrides:
   virtual void OnWindowActivated(aura::Window* gained_active,
diff --git a/ash/wm/screen_dimmer.cc b/ash/wm/screen_dimmer.cc
index 3cb4e96c20f983..814620a2cf5792 100644
--- a/ash/wm/screen_dimmer.cc
+++ b/ash/wm/screen_dimmer.cc
@@ -28,11 +28,11 @@ const int kDimmingTransitionMs = 200;
 ScreenDimmer::ScreenDimmer(aura::RootWindow* root_window)
     : root_window_(root_window),
       currently_dimming_(false) {
-  root_window_->AddRootWindowObserver(this);
+  root_window_->AddObserver(this);
 }
 
 ScreenDimmer::~ScreenDimmer() {
-  root_window_->RemoveRootWindowObserver(this);
+  root_window_->RemoveObserver(this);
 }
 
 void ScreenDimmer::SetDimming(bool should_dim) {
@@ -58,8 +58,9 @@ void ScreenDimmer::SetDimming(bool should_dim) {
   dimming_layer_->SetOpacity(should_dim ? kDimmingLayerOpacity : 0.0f);
 }
 
-void ScreenDimmer::OnRootWindowResized(const aura::RootWindow* root,
-                                       const gfx::Size& old_size) {
+void ScreenDimmer::OnWindowBoundsChanged(aura::Window* root,
+                                         const gfx::Rect& old_bounds,
+                                         const gfx::Rect& new_bounds) {
   if (dimming_layer_)
     dimming_layer_->SetBounds(gfx::Rect(root->bounds().size()));
 }
diff --git a/ash/wm/screen_dimmer.h b/ash/wm/screen_dimmer.h
index 9d581fa473f34b..476c27449a30e0 100644
--- a/ash/wm/screen_dimmer.h
+++ b/ash/wm/screen_dimmer.h
@@ -9,7 +9,7 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
-#include "ui/aura/root_window_observer.h"
+#include "ui/aura/window_observer.h"
 
 namespace aura {
 class RootWindow;
@@ -29,7 +29,7 @@ namespace internal {
 // briefly dim the screen (e.g. to indicate to the user that we're
 // about to suspend a machine that lacks an internal backlight that
 // can be adjusted).
-class ASH_EXPORT ScreenDimmer : public aura::RootWindowObserver {
+class ASH_EXPORT ScreenDimmer : public aura::WindowObserver {
  public:
   class TestApi {
    public:
@@ -49,9 +49,10 @@ class ASH_EXPORT ScreenDimmer : public aura::RootWindowObserver {
   // Dim or undim the root window.
   void SetDimming(bool should_dim);
 
-  // aura::RootWindowObserver overrides:
-  virtual void OnRootWindowResized(const aura::RootWindow* root,
-                                   const gfx::Size& old_size) OVERRIDE;
+  // aura::WindowObserver overrides:
+  virtual void OnWindowBoundsChanged(aura::Window* root_window,
+                                     const gfx::Rect& old_bounds,
+                                     const gfx::Rect& new_bounds) OVERRIDE;
 
  private:
   friend class TestApi;
diff --git a/ash/wm/system_background_controller.cc b/ash/wm/system_background_controller.cc
index 8f06f02e7c1e89..588073546decd9 100644
--- a/ash/wm/system_background_controller.cc
+++ b/ash/wm/system_background_controller.cc
@@ -25,7 +25,7 @@ SystemBackgroundController::SystemBackgroundController(
     SkColor color)
     : root_window_(root_window),
       layer_(new ui::Layer(ui::LAYER_SOLID_COLOR)) {
-  root_window_->AddRootWindowObserver(this);
+  root_window_->AddObserver(this);
   layer_->SetColor(color);
 
   ui::Layer* root_layer = root_window_->layer();
@@ -35,16 +35,17 @@ SystemBackgroundController::SystemBackgroundController(
 }
 
 SystemBackgroundController::~SystemBackgroundController() {
-  root_window_->RemoveRootWindowObserver(this);
+  root_window_->RemoveObserver(this);
 }
 
 void SystemBackgroundController::SetColor(SkColor color) {
   layer_->SetColor(color);
 }
 
-void SystemBackgroundController::OnRootWindowResized(
-    const aura::RootWindow* root,
-    const gfx::Size& old_size) {
+void SystemBackgroundController::OnWindowBoundsChanged(
+    aura::Window* root,
+    const gfx::Rect& old_bounds,
+    const gfx::Rect& new_bounds) {
   DCHECK_EQ(root_window_, root);
   layer_->SetBounds(gfx::Rect(root_window_->layer()->bounds().size()));
 }
diff --git a/ash/wm/system_background_controller.h b/ash/wm/system_background_controller.h
index 6da656345bd5be..36382646b3c1fb 100644
--- a/ash/wm/system_background_controller.h
+++ b/ash/wm/system_background_controller.h
@@ -11,7 +11,7 @@
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "third_party/skia/include/core/SkColor.h"
-#include "ui/aura/root_window_observer.h"
+#include "ui/aura/window_observer.h"
 
 namespace aura {
 class RootWindow;
@@ -30,16 +30,17 @@ namespace internal {
 // desktop background image is loaded at startup, or when we scale down all of
 // the other layers as part of a power-button or window-management animation).
 // It should never be transformed or restacked.
-class SystemBackgroundController : public aura::RootWindowObserver {
+class SystemBackgroundController : public aura::WindowObserver {
  public:
   SystemBackgroundController(aura::RootWindow* root_window, SkColor color);
   virtual ~SystemBackgroundController();
 
   void SetColor(SkColor color);
 
-  // aura::RootWindowObserver overrides:
-  virtual void OnRootWindowResized(const aura::RootWindow* root,
-                                   const gfx::Size& old_size) OVERRIDE;
+  // aura::WindowObserver overrides:
+  virtual void OnWindowBoundsChanged(aura::Window* root,
+                                     const gfx::Rect& old_bounds,
+                                     const gfx::Rect& new_bounds) OVERRIDE;
 
  private:
   class HostContentLayerDelegate;
diff --git a/ash/wm/workspace/workspace_layout_manager.cc b/ash/wm/workspace/workspace_layout_manager.cc
index ed0a913f49c611..cf8f4930db7dd3 100644
--- a/ash/wm/workspace/workspace_layout_manager.cc
+++ b/ash/wm/workspace/workspace_layout_manager.cc
@@ -87,15 +87,12 @@ WorkspaceLayoutManager::WorkspaceLayoutManager(Workspace* workspace)
       work_area_(ScreenAsh::GetDisplayWorkAreaBoundsInParent(
                      workspace->window()->parent())) {
   Shell::GetInstance()->AddShellObserver(this);
-  root_window_->AddRootWindowObserver(this);
   root_window_->AddObserver(this);
 }
 
 WorkspaceLayoutManager::~WorkspaceLayoutManager() {
-  if (root_window_) {
+  if (root_window_)
     root_window_->RemoveObserver(this);
-    root_window_->RemoveRootWindowObserver(this);
-  }
   for (WindowSet::const_iterator i = windows_.begin(); i != windows_.end(); ++i)
     (*i)->RemoveObserver(this);
   Shell::GetInstance()->RemoveShellObserver(this);
@@ -158,11 +155,6 @@ void WorkspaceLayoutManager::SetChildBounds(
   workspace_manager()->OnWorkspaceWindowChildBoundsChanged(workspace_, child);
 }
 
-void WorkspaceLayoutManager::OnRootWindowResized(const aura::RootWindow* root,
-                                                 const gfx::Size& old_size) {
-  AdjustWindowSizesForScreenChange(ADJUST_WINDOW_SCREEN_SIZE_CHANGED);
-}
-
 void WorkspaceLayoutManager::OnDisplayWorkAreaInsetsChanged() {
   if (workspace_manager()->active_workspace_ == workspace_) {
     const gfx::Rect work_area(ScreenAsh::GetDisplayWorkAreaBoundsInParent(
@@ -261,6 +253,14 @@ void WorkspaceLayoutManager::OnWindowDestroying(aura::Window* window) {
   }
 }
 
+void WorkspaceLayoutManager::OnWindowBoundsChanged(
+    aura::Window* window,
+    const gfx::Rect& old_bounds,
+    const gfx::Rect& new_bounds) {
+  if (root_window_ == window)
+    AdjustWindowSizesForScreenChange(ADJUST_WINDOW_SCREEN_SIZE_CHANGED);
+}
+
 void WorkspaceLayoutManager::ShowStateChanged(
     Window* window,
     ui::WindowShowState last_show_state,
diff --git a/ash/wm/workspace/workspace_layout_manager.h b/ash/wm/workspace/workspace_layout_manager.h
index 50942682f7dbc7..65246d2dc9ccde 100644
--- a/ash/wm/workspace/workspace_layout_manager.h
+++ b/ash/wm/workspace/workspace_layout_manager.h
@@ -12,7 +12,6 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ui/aura/layout_manager.h"
-#include "ui/aura/root_window_observer.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/aura/window_observer.h"
 #include "ui/gfx/rect.h"
@@ -39,7 +38,6 @@ class WorkspaceManager;
 // See if I can refactor the code to make it easier to share common bits.
 class ASH_EXPORT WorkspaceLayoutManager
     : public aura::LayoutManager,
-      public aura::RootWindowObserver,
       public ash::ShellObserver,
       public aura::WindowObserver {
  public:
@@ -57,10 +55,6 @@ class ASH_EXPORT WorkspaceLayoutManager
   virtual void SetChildBounds(aura::Window* child,
                               const gfx::Rect& requested_bounds) OVERRIDE;
 
-  // RootWindowObserver overrides:
-  virtual void OnRootWindowResized(const aura::RootWindow* root,
-                                   const gfx::Size& old_size) OVERRIDE;
-
   // ash::ShellObserver overrides:
   virtual void OnDisplayWorkAreaInsetsChanged() OVERRIDE;
 
@@ -69,6 +63,9 @@ class ASH_EXPORT WorkspaceLayoutManager
                                        const void* key,
                                        intptr_t old) OVERRIDE;
   virtual void OnWindowDestroying(aura::Window* window) OVERRIDE;
+  virtual void OnWindowBoundsChanged(aura::Window* window,
+                                     const gfx::Rect& old_bounds,
+                                     const gfx::Rect& new_bounds) OVERRIDE;
 
  private:
   typedef std::set<aura::Window*> WindowSet;
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 fedd08631eaf4f..60788058732115 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -2670,8 +2670,9 @@ void RenderWidgetHostViewAura::OnWindowFocused(aura::Window* gained_focus,
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewAura, aura::RootWindowObserver implementation:
 
-void RenderWidgetHostViewAura::OnRootWindowMoved(const aura::RootWindow* root,
-                                                 const gfx::Point& new_origin) {
+void RenderWidgetHostViewAura::OnRootWindowHostMoved(
+    const aura::RootWindow* root,
+    const gfx::Point& new_origin) {
   UpdateScreenInfo(window_);
 }
 
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.h b/content/browser/renderer_host/render_widget_host_view_aura.h
index d87eeb29ab890a..7128e9855988fa 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.h
+++ b/content/browser/renderer_host/render_widget_host_view_aura.h
@@ -320,8 +320,8 @@ class RenderWidgetHostViewAura
                                aura::Window* lost_focus) OVERRIDE;
 
   // Overridden from aura::RootWindowObserver:
-  virtual void OnRootWindowMoved(const aura::RootWindow* root,
-                                 const gfx::Point& new_origin) OVERRIDE;
+  virtual void OnRootWindowHostMoved(const aura::RootWindow* root,
+                                     const gfx::Point& new_origin) OVERRIDE;
 
 #if defined(OS_WIN)
   // Sets the cutout rects from constrained windows. These are rectangles that
diff --git a/content/browser/web_contents/web_contents_view_aura.cc b/content/browser/web_contents/web_contents_view_aura.cc
index f9273355042d38..dedc81c1accbfe 100644
--- a/content/browser/web_contents/web_contents_view_aura.cc
+++ b/content/browser/web_contents/web_contents_view_aura.cc
@@ -497,8 +497,8 @@ class WebContentsViewAura::WindowObserver
   }
 
   // Overridden RootWindowObserver:
-  virtual void OnRootWindowMoved(const aura::RootWindow* root,
-                                 const gfx::Point& new_origin) OVERRIDE {
+  virtual void OnRootWindowHostMoved(const aura::RootWindow* root,
+                                     const gfx::Point& new_origin) OVERRIDE {
     // This is for the desktop case (i.e. Aura desktop).
     SendScreenRects();
   }
diff --git a/ui/aura/root_window.cc b/ui/aura/root_window.cc
index e4a0feea324ee6..d812f5294f8c8e 100644
--- a/ui/aura/root_window.cc
+++ b/ui/aura/root_window.cc
@@ -197,7 +197,7 @@ void RootWindow::Init() {
   Window::Init(ui::LAYER_NOT_DRAWN);
   compositor()->SetRootLayer(layer());
   transformer_.reset(new SimpleRootWindowTransformer(this, gfx::Transform()));
-  UpdateWindowSize(host_->GetBounds().size());
+  UpdateRootWindowSize(GetHostSize());
   Env::GetInstance()->NotifyRootWindowInitialized(this);
   Show();
 }
@@ -539,10 +539,10 @@ void RootWindow::SetRootWindowTransformer(
   transformer_ = transformer.Pass();
   host_->SetInsets(transformer_->GetHostInsets());
   Window::SetTransform(transformer_->GetTransform());
-  // If the layer is not animating, then we need to update the host size
-  // immediately.
+  // If the layer is not animating, then we need to update the root window
+  // size immediately.
   if (!layer()->GetAnimator()->is_animating())
-    OnHostResized(host_->GetBounds().size());
+    UpdateRootWindowSize(GetHostSize());
 }
 
 gfx::Transform RootWindow::GetRootTransform() const {
@@ -845,7 +845,7 @@ void RootWindow::CleanupGestureRecognizerState(Window* window) {
   }
 }
 
-void RootWindow::UpdateWindowSize(const gfx::Size& host_size) {
+void RootWindow::UpdateRootWindowSize(const gfx::Size& host_size) {
   SetBounds(transformer_->GetRootWindowBounds(host_size));
 }
 
@@ -869,7 +869,7 @@ bool RootWindow::DispatchCancelTouchEvent(ui::TouchEvent* event) {
 
 void RootWindow::OnLayerAnimationEnded(
     ui::LayerAnimationSequence* animation) {
-  OnHostResized(host_->GetBounds().size());
+  UpdateRootWindowSize(GetHostSize());
 }
 
 void RootWindow::OnLayerAnimationScheduled(
@@ -987,7 +987,7 @@ void RootWindow::OnHostPaint(const gfx::Rect& damage_rect) {
 
 void RootWindow::OnHostMoved(const gfx::Point& origin) {
   FOR_EACH_OBSERVER(RootWindowObserver, observers_,
-                    OnRootWindowMoved(this, origin));
+                    OnRootWindowHostMoved(this, origin));
 }
 
 void RootWindow::OnHostResized(const gfx::Size& size) {
@@ -996,13 +996,11 @@ void RootWindow::OnHostResized(const gfx::Size& size) {
   // Get the latest scale from display because it might have been changed.
   compositor_->SetScaleAndSize(GetDeviceScaleFactorFromDisplay(this), size);
 
-  // The layer, and all the observers should be notified of the
+  // The layer, and the observers should be notified of the
   // transformed size of the root window.
-  gfx::Size old(bounds().size());
-  UpdateWindowSize(size);
-  // TODO(oshima): Rename this to OnHostWindowResized.
+  UpdateRootWindowSize(size);
   FOR_EACH_OBSERVER(RootWindowObserver, observers_,
-                    OnRootWindowResized(this, old));
+                    OnRootWindowHostResized(this));
 }
 
 float RootWindow::GetDeviceScaleFactor() {
diff --git a/ui/aura/root_window.h b/ui/aura/root_window.h
index dc1918e26b28a0..0d5a0a24a4746e 100644
--- a/ui/aura/root_window.h
+++ b/ui/aura/root_window.h
@@ -353,7 +353,7 @@ class AURA_EXPORT RootWindow : public ui::CompositorDelegate,
 
   // Updates the root window's size using |host_size|, current
   // transform and insets.
-  void UpdateWindowSize(const gfx::Size& host_size);
+  void UpdateRootWindowSize(const gfx::Size& host_size);
 
   // Overridden from ui::EventDispatcherDelegate.
   virtual bool CanDispatchToTarget(EventTarget* target) OVERRIDE;
diff --git a/ui/aura/root_window_observer.h b/ui/aura/root_window_observer.h
index 81dcad95f55ff4..bfb8e65c518a6a 100644
--- a/ui/aura/root_window_observer.h
+++ b/ui/aura/root_window_observer.h
@@ -18,13 +18,12 @@ class Window;
 
 class AURA_EXPORT RootWindowObserver {
  public:
-  // Invoked after the RootWindow is resized.
-  virtual void OnRootWindowResized(const RootWindow* root,
-                                   const gfx::Size& old_size) {}
+  // Invoked after the RootWindow's host has been resized.
+  virtual void OnRootWindowHostResized(const RootWindow* root) {}
 
-  // Invoked after the RootWindow has been moved on screen.
-  virtual void OnRootWindowMoved(const RootWindow* root,
-                                 const gfx::Point& new_origin) {}
+  // Invoked after the RootWindow's host has been moved on screen.
+  virtual void OnRootWindowHostMoved(const RootWindow* root,
+                                     const gfx::Point& new_origin) {}
 
   // Invoked when the native windowing system sends us a request to close our
   // window.