Add flag for disabling login wallpaper dimming and blur

Add a switch for convenience of debugging issues such as
crbug.com/776613.

Also place the flag under about://flag because we may need to turn off
blur in non-dev mode for debugging purpose.

Bug: NONE
Change-Id: Ie6114f5a504f836f28ff3df3b749560e0155b1f7
Reviewed-on: https://chromium-review.googlesource.com/752063
Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#514337}

ash/public/cpp/ash_switches.cc

@@ -18,6 +18,9 @@ const char kAshDebugShortcuts[] = "ash-debug-shortcuts";
 // Enable keyboard shortcuts used by developers only.
 const char kAshDeveloperShortcuts[] = "ash-dev-shortcuts";
 
+// Disables the dimming and blur of the wallpaper on login and lock screens.
+const char kAshDisableLoginDimAndBlur[] = "ash-disable-login-dim-and-blur";
+
 // Use a single in-process shelf data model shared between Chrome and Ash.
 // This only applies to the Classic Ash and Mus configs; synchronization between
 // two models is required when running the Mash config via --mash.

ash/public/cpp/ash_switches.h

@@ -19,6 +19,7 @@ namespace switches {
 ASH_PUBLIC_EXPORT extern const char kAshConstrainPointerToRoot[];
 ASH_PUBLIC_EXPORT extern const char kAshDebugShortcuts[];
 ASH_PUBLIC_EXPORT extern const char kAshDeveloperShortcuts[];
+ASH_PUBLIC_EXPORT extern const char kAshDisableLoginDimAndBlur[];
 ASH_PUBLIC_EXPORT extern const char kAshDisableShelfModelSynchronization[];
 ASH_PUBLIC_EXPORT extern const char kAshDisableSmoothScreenRotation[];
 ASH_PUBLIC_EXPORT extern const char kAshDisableTabletAutohideTitlebars[];

ash/wallpaper/wallpaper_controller.cc

@@ -374,6 +374,12 @@ void WallpaperController::OpenSetWallpaperPage() {
   }
 }
 
+bool WallpaperController::ShouldApplyDimAndBlur() const {
+  return Shell::Get()->session_controller()->IsUserSessionBlocked() &&
+         !base::CommandLine::ForCurrentProcess()->HasSwitch(
+             switches::kAshDisableLoginDimAndBlur);
+}
+
 void WallpaperController::AddObserver(
     mojom::WallpaperObserverAssociatedPtrInfo observer) {
   mojom::WallpaperObserverAssociatedPtr observer_ptr;
@@ -427,7 +433,7 @@ void WallpaperController::InstallDesktopController(aura::Window* root_window) {
       return;
   }
 
-  if (Shell::Get()->session_controller()->IsUserSessionBlocked())
+  if (ShouldApplyDimAndBlur())
     component->SetWallpaperBlur(login_constants::kBlurSigma);
 
   RootWindowController* controller =

ash/wallpaper/wallpaper_controller.h

@@ -127,6 +127,10 @@ class ASH_EXPORT WallpaperController
   // Opens the set wallpaper page in the browser.
   void OpenSetWallpaperPage();
 
+  // Wallpaper should be dimmed and blurred when showing login, lock, OOBE or
+  // add user screens.
+  bool ShouldApplyDimAndBlur() const;
+
   // mojom::WallpaperController overrides:
   void AddObserver(mojom::WallpaperObserverAssociatedPtrInfo observer) override;
   void SetWallpaperPicker(mojom::WallpaperPickerPtr picker) override;

ash/wallpaper/wallpaper_view.cc

@@ -160,7 +160,7 @@ void WallpaperView::OnPaint(gfx::Canvas* canvas) {
     return;
 
   cc::PaintFlags flags;
-  if (Shell::Get()->session_controller()->IsUserSessionBlocked()) {
+  if (controller->ShouldApplyDimAndBlur()) {
     flags.setColorFilter(SkColorFilter::MakeModeFilter(
         GetWallpaperDarkenColor(), SkBlendMode::kDarken));
   }

chrome/browser/about_flags.cc

@@ -3552,6 +3552,11 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kAshEnableKeyboardShortcutViewerName,
      flag_descriptions::kAshEnableKeyboardShortcutViewerDescription, kOsCrOS,
      SINGLE_VALUE_TYPE(ash::switches::kAshEnableKeyboardShortcutViewer)},
+
+    {"ash-disable-login-dim-and-blur",
+     flag_descriptions::kAshDisableLoginDimAndBlurName,
+     flag_descriptions::kAshDisableLoginDimAndBlurDescription, kOsCrOS,
+     SINGLE_DISABLE_VALUE_TYPE(ash::switches::kAshDisableLoginDimAndBlur)},
 #endif  // OS_CHROMEOS
 
 #if defined(OS_CHROMEOS)

chrome/browser/flag_descriptions.cc

@@ -2425,8 +2425,7 @@ const char kDisableSystemTimezoneAutomaticDetectionDescription[] =
 
 const char kEnableBackgroundBlurName[] = "Enable background blur.";
 const char kEnableBackgroundBlurDescription[] =
-    "Enables background blur for the Peeking Launcher, Lock Screen, and Tab "
-    "Switcher.";
+    "Enables background blur for the Peeking Launcher and Tab Switcher.";
 
 const char kEnableAndroidWallpapersAppName[] = "Android Wallpapers App";
 const char kEnableAndroidWallpapersAppDescription[] =
@@ -2771,6 +2770,11 @@ const char kWebrtcH264WithOpenh264FfmpegDescription[] =
 
 #if defined(OS_CHROMEOS)
 
+const char kAshDisableLoginDimAndBlurName[] =
+    "Disable dimming and blur on login screen.";
+const char kAshDisableLoginDimAndBlurDescription[] =
+    "Disable dimming and blur on login screen.";
+
 const char kAshDisableSmoothScreenRotationName[] =
     "Disable smooth rotation animations.";
 const char kAshDisableSmoothScreenRotationDescription[] =

chrome/browser/flag_descriptions.h

@@ -1714,6 +1714,9 @@ extern const char kWebrtcH264WithOpenh264FfmpegDescription[];
 
 #if defined(OS_CHROMEOS)
 
+extern const char kAshDisableLoginDimAndBlurName[];
+extern const char kAshDisableLoginDimAndBlurDescription[];
+
 extern const char kAshDisableSmoothScreenRotationName[];
 extern const char kAshDisableSmoothScreenRotationDescription[];
 

tools/metrics/histograms/enums.xml

@@ -24259,6 +24259,7 @@ from previous Chrome versions.
   <int value="-1487243228" label="NewUsbBackend:disabled"/>
   <int value="-1482685863" label="enable-request-tablet-site"/>
   <int value="-1480926949" label="MaterialDesignBookmarks:enabled"/>
+  <int value="-1480866718" label="ash-disable-login-dim-and-blur"/>
   <int value="-1478876902" label="disable-permission-action-reporting"/>
   <int value="-1473668019" label="token-binding:disabled"/>
   <int value="-1473136627" label="enable-web-payments"/>