Merge 284026 "Add app.window.alphaEnabled() and onAlphaEnabledCh..."

> Add app.window.alphaEnabled() and onAlphaEnabledChanged.
> 
> This allows an app to determine whether a window created with
> "transparent_background" will work as expected.
> 
> This also allows the app to detect when "transparent_background" might
> stop working, e.g. when Windows changes from Aero to Classic.
> 
> This also fixes the bug where "transparent_background" windows
> created in Classic render as black rectangles.
> 
> BUG=260810
> 
> Review URL: https://codereview.chromium.org/375183002

TBR=jackhou@chromium.org

Review URL: https://codereview.chromium.org/412033002

git-svn-id: svn://svn.chromium.org/chrome/branches/2062/src@285044 0039d316-1c4b-4281-b951-d872f2087c98

26 files changed, 97 insertions, 7 deletions

diff --git a/apps/app_window.cc b/apps/app_window.cc
index 814d2e0..427cdc6 100644
--- a/apps/app_window.cc
+++ b/apps/app_window.cc
@@ -245,7 +245,8 @@ AppWindow::AppWindow(BrowserContext* context,
       has_been_shown_(false),
       can_send_events_(false),
       is_hidden_(false),
-      cached_always_on_top_(false) {
+      cached_always_on_top_(false),
+      requested_transparent_background_(false) {
   extensions::ExtensionsBrowserClient* client =
       extensions::ExtensionsBrowserClient::Get();
   CHECK(!client->IsGuestSession(context) || context->IsOffTheRecord())
@@ -284,6 +285,8 @@ void AppWindow::Init(const GURL& url,
   if (new_params.state == ui::SHOW_STATE_FULLSCREEN)
     new_params.always_on_top = false;
 
+  requested_transparent_background_ = new_params.transparent_background;
+
   native_app_window_.reset(delegate_->CreateNativeAppWindow(this, new_params));
 
   // Prevent the browser process from shutting down while this window exists.
@@ -751,6 +754,9 @@ void AppWindow::GetSerializedState(base::DictionaryValue* properties) const {
   properties->SetBoolean("maximized", native_app_window_->IsMaximized());
   properties->SetBoolean("alwaysOnTop", IsAlwaysOnTop());
   properties->SetBoolean("hasFrameColor", native_app_window_->HasFrameColor());
+  properties->SetBoolean("alphaEnabled",
+                         requested_transparent_background_ &&
+                             native_app_window_->CanHaveAlphaEnabled());
 
   // These properties are undocumented and are to enable testing. Alpha is
   // removed to
diff --git a/apps/app_window.h b/apps/app_window.h
index f2e0e98..216ee3c 100644
--- a/apps/app_window.h
+++ b/apps/app_window.h
@@ -362,6 +362,11 @@ class AppWindow : public content::NotificationObserver,
   // app.
   void WindowEventsReady();
 
+  // Whether the app window wants a transparent background.
+  bool requested_transparent_background() const {
+    return requested_transparent_background_;
+  }
+
  protected:
   virtual ~AppWindow();
 
@@ -558,6 +563,9 @@ class AppWindow : public content::NotificationObserver,
   // taskbar.
   bool cached_always_on_top_;
 
+  // Whether |transparent_background| was set in the CreateParams.
+  bool requested_transparent_background_;
+
   DISALLOW_COPY_AND_ASSIGN(AppWindow);
 };
 
diff --git a/apps/ui/native_app_window.h b/apps/ui/native_app_window.h
index cde4c1d..fd0cc26 100644
--- a/apps/ui/native_app_window.h
+++ b/apps/ui/native_app_window.h
@@ -87,6 +87,10 @@ class NativeAppWindow : public ui::BaseWindow,
   virtual void SetContentSizeConstraints(const gfx::Size& min_size,
                                          const gfx::Size& max_size) = 0;
 
+  // Returns false if the underlying native window ignores alpha transparency
+  // when compositing.
+  virtual bool CanHaveAlphaEnabled() const = 0;
+
   virtual ~NativeAppWindow() {}
 };
 
diff --git a/apps/ui/views/native_app_window_views.cc b/apps/ui/views/native_app_window_views.cc
index 62b941d..da84d8a 100644
--- a/apps/ui/views/native_app_window_views.cc
+++ b/apps/ui/views/native_app_window_views.cc
@@ -27,14 +27,12 @@ NativeAppWindowViews::NativeAppWindowViews()
       web_view_(NULL),
       widget_(NULL),
       frameless_(false),
-      transparent_background_(false),
       resizable_(false) {}
 
 void NativeAppWindowViews::Init(AppWindow* app_window,
                                 const AppWindow::CreateParams& create_params) {
   app_window_ = app_window;
   frameless_ = create_params.frame == AppWindow::FRAME_NONE;
-  transparent_background_ = create_params.transparent_background;
   resizable_ = create_params.resizable;
   size_constraints_.set_minimum_size(
       create_params.GetContentMinimumSize(gfx::Insets()));
@@ -53,6 +51,10 @@ NativeAppWindowViews::~NativeAppWindowViews() {
   web_view_->SetWebContents(NULL);
 }
 
+void NativeAppWindowViews::OnCanHaveAlphaEnabledChanged() {
+  app_window_->OnNativeWindowChanged();
+}
+
 void NativeAppWindowViews::InitializeWindow(
     AppWindow* app_window,
     const AppWindow::CreateParams& create_params) {
@@ -260,7 +262,8 @@ void NativeAppWindowViews::OnWidgetActivationChanged(views::Widget* widget,
 
 void NativeAppWindowViews::RenderViewCreated(
     content::RenderViewHost* render_view_host) {
-  if (transparent_background_) {
+  if (app_window_->requested_transparent_background() &&
+      CanHaveAlphaEnabled()) {
     content::RenderWidgetHostView* view = render_view_host->GetView();
     DCHECK(view);
     view->SetBackgroundOpaque(false);
@@ -398,4 +401,8 @@ void NativeAppWindowViews::SetContentSizeConstraints(
   size_constraints_.set_maximum_size(max_size);
 }
 
+bool NativeAppWindowViews::CanHaveAlphaEnabled() const {
+  return widget_->IsTranslucentWindowOpacitySupported();
+}
+
 }  // namespace apps
diff --git a/apps/ui/views/native_app_window_views.h b/apps/ui/views/native_app_window_views.h
index bdebfde..917feca 100644
--- a/apps/ui/views/native_app_window_views.h
+++ b/apps/ui/views/native_app_window_views.h
@@ -52,6 +52,9 @@ class NativeAppWindowViews : public NativeAppWindow,
   void Init(AppWindow* app_window,
             const AppWindow::CreateParams& create_params);
 
+  // Signal that CanHaveTransparentBackground has changed.
+  void OnCanHaveAlphaEnabledChanged();
+
   views::Widget* widget() { return widget_; }
 
   void set_window_for_testing(views::Widget* window) { widget_ = window; }
@@ -156,6 +159,7 @@ class NativeAppWindowViews : public NativeAppWindow,
   virtual gfx::Size GetContentMaximumSize() const OVERRIDE;
   virtual void SetContentSizeConstraints(const gfx::Size& min_size,
                                          const gfx::Size& max_size) OVERRIDE;
+  virtual bool CanHaveAlphaEnabled() const OVERRIDE;
 
   // web_modal::WebContentsModalDialogHost implementation.
   virtual gfx::NativeView GetHostView() const OVERRIDE;
@@ -177,7 +181,6 @@ class NativeAppWindowViews : public NativeAppWindow,
   scoped_ptr<SkRegion> draggable_region_;
 
   bool frameless_;
-  bool transparent_background_;
   bool resizable_;
   apps::SizeConstraints size_constraints_;
 
diff --git a/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.h b/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.h
index cea4db8..c896571 100644
--- a/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.h
+++ b/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.h
@@ -135,6 +135,7 @@ class NativeAppWindowCocoa : public apps::NativeAppWindow,
   virtual SkColor ActiveFrameColor() const OVERRIDE;
   virtual SkColor InactiveFrameColor() const OVERRIDE;
   virtual gfx::Insets GetFrameInsets() const OVERRIDE;
+  virtual bool CanHaveAlphaEnabled() const OVERRIDE;
 
   // These are used to simulate Mac-style hide/show. Since windows can be hidden
   // and shown using the app.window API, this sets is_hidden_with_app_ to
diff --git a/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm b/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm
index 9b45321..e3bdc70 100644
--- a/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm
+++ b/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm
@@ -799,6 +799,10 @@ gfx::Insets NativeAppWindowCocoa::GetFrameInsets() const {
   return frame_rect.InsetsFrom(content_rect);
 }
 
+bool NativeAppWindowCocoa::CanHaveAlphaEnabled() const {
+  return false;
+}
+
 gfx::NativeView NativeAppWindowCocoa::GetHostView() const {
   NOTIMPLEMENTED();
   return NULL;
diff --git a/chrome/browser/ui/views/apps/app_window_desktop_window_tree_host_win.cc b/chrome/browser/ui/views/apps/app_window_desktop_window_tree_host_win.cc
index b2301e6..f6a8139 100644
--- a/chrome/browser/ui/views/apps/app_window_desktop_window_tree_host_win.cc
+++ b/chrome/browser/ui/views/apps/app_window_desktop_window_tree_host_win.cc
@@ -48,6 +48,7 @@ bool AppWindowDesktopWindowTreeHostWin::GetClientAreaInsets(
 void AppWindowDesktopWindowTreeHostWin::HandleFrameChanged() {
   // We need to update the glass region on or off before the base class adjusts
   // the window region.
+  app_window_->OnCanHaveAlphaEnabledChanged();
   UpdateDWMFrame();
   DesktopWindowTreeHostWin::HandleFrameChanged();
 }
diff --git a/chrome/common/extensions/api/app_current_window_internal.idl b/chrome/common/extensions/api/app_current_window_internal.idl
index a8a1cd5..890e75b 100644
--- a/chrome/common/extensions/api/app_current_window_internal.idl
+++ b/chrome/common/extensions/api/app_current_window_internal.idl
@@ -61,6 +61,7 @@
     static void onMinimized();
     static void onMaximized();
     static void onRestored();
+    static void onAlphaEnabledChanged();
     // Only sent in tests.
     static void onWindowShownForTests();
   };
diff --git a/chrome/common/extensions/api/app_window.idl b/chrome/common/extensions/api/app_window.idl
index b08037b..26922d7 100644
--- a/chrome/common/extensions/api/app_window.idl
+++ b/chrome/common/extensions/api/app_window.idl
@@ -351,6 +351,10 @@ namespace app.window {
     // <code>"alwaysOnTopWindows"</code> permission.
     static void setAlwaysOnTop(boolean alwaysOnTop);
 
+    // Can the window use alpha transparency?
+    // TODO(jackhou): Document this properly before going to stable.
+    [nodoc] static boolean alphaEnabled();
+
     // The JavaScript 'window' object for the created child.
     [instanceOf=Window] object contentWindow;
 
@@ -433,6 +437,9 @@ namespace app.window {
     // Fired when the window is restored from being minimized or maximized.
     [nocompile] static void onRestored();
 
+    // Fired when the window's ability to use alpha transparency changes.
+    [nocompile, nodoc] static void onAlphaEnabledChanged();
+
     // Event for testing. Lets tests wait until a window has been shown.
     [nocompile, nodoc] static void onWindowFirstShown();
   };
diff --git a/chrome/renderer/resources/extensions/app_window_custom_bindings.js b/chrome/renderer/resources/extensions/app_window_custom_bindings.js
index 99ca8bc..c666d32 100644
--- a/chrome/renderer/resources/extensions/app_window_custom_bindings.js
+++ b/chrome/renderer/resources/extensions/app_window_custom_bindings.js
@@ -241,6 +241,9 @@ appWindow.registerCustomHook(function(bindingsAPI) {
     AppWindow.prototype.isAlwaysOnTop = function() {
       return appWindowData.alwaysOnTop;
     };
+    AppWindow.prototype.alphaEnabled = function() {
+      return appWindowData.alphaEnabled;
+    }
     AppWindow.prototype.handleWindowFirstShownForTests = function(callback) {
       // This allows test apps to get have their callback run even if they
       // call this after the first show has happened.
@@ -301,7 +304,8 @@ appWindow.registerCustomHook(function(bindingsAPI) {
       alwaysOnTop: params.alwaysOnTop,
       hasFrameColor: params.hasFrameColor,
       activeFrameColor: params.activeFrameColor,
-      inactiveFrameColor: params.inactiveFrameColor
+      inactiveFrameColor: params.inactiveFrameColor,
+      alphaEnabled: params.alphaEnabled
     };
     currentAppWindow = new AppWindow;
   });
@@ -348,6 +352,9 @@ function updateAppWindowProperties(update) {
       (oldData.minimized && !update.minimized) ||
       (oldData.maximized && !update.maximized))
     dispatchEventIfExists(currentWindow, "onRestored");
+
+  if (oldData.alphaEnabled !== update.alphaEnabled)
+    dispatchEventIfExists(currentWindow, "onAlphaEnabledChanged");
 };
 
 function onAppWindowShownForTests() {
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 60458c7..1a45795 100644
--- a/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
+++ b/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
@@ -932,6 +932,11 @@ void DesktopNativeWidgetAura::OnRootViewLayout() const {
     desktop_window_tree_host_->OnRootViewLayout();
 }
 
+bool DesktopNativeWidgetAura::IsTranslucentWindowOpacitySupported() const {
+  return content_window_ &&
+      desktop_window_tree_host_->IsTranslucentWindowOpacitySupported();
+}
+
 void DesktopNativeWidgetAura::RepostNativeEvent(gfx::NativeEvent native_event) {
   OnEvent(native_event);
 }
diff --git a/ui/views/widget/desktop_aura/desktop_native_widget_aura.h b/ui/views/widget/desktop_aura/desktop_native_widget_aura.h
index f265814..f005f36 100644
--- a/ui/views/widget/desktop_aura/desktop_native_widget_aura.h
+++ b/ui/views/widget/desktop_aura/desktop_native_widget_aura.h
@@ -178,6 +178,7 @@ class VIEWS_EXPORT DesktopNativeWidgetAura
   virtual void SetVisibilityChangedAnimationsEnabled(bool value) OVERRIDE;
   virtual ui::NativeTheme* GetNativeTheme() const OVERRIDE;
   virtual void OnRootViewLayout() const OVERRIDE;
+  virtual bool IsTranslucentWindowOpacitySupported() const OVERRIDE;
   virtual void RepostNativeEvent(gfx::NativeEvent native_event) OVERRIDE;
 
   // Overridden from aura::WindowDelegate:
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host.h b/ui/views/widget/desktop_aura/desktop_window_tree_host.h
index 26925b67..9ccb672 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host.h
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host.h
@@ -153,6 +153,9 @@ class VIEWS_EXPORT DesktopWindowTreeHost {
   // Returns true if the Widget was closed but is still showing because of
   // animations.
   virtual bool IsAnimatingClosed() const = 0;
+
+  // Returns true if the Widget supports translucency.
+  virtual bool IsTranslucentWindowOpacitySupported() const = 0;
 };
 
 }  // namespace views
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc b/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
index fc2bda6..6347526 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
@@ -365,7 +365,7 @@ void DesktopWindowTreeHostWin::SetVisibilityChangedAnimationsEnabled(
 }
 
 bool DesktopWindowTreeHostWin::ShouldUseNativeFrame() const {
-  return ui::win::IsAeroGlassEnabled();
+  return IsTranslucentWindowOpacitySupported();
 }
 
 bool DesktopWindowTreeHostWin::ShouldWindowContentsBeTransparent() const {
@@ -427,6 +427,10 @@ bool DesktopWindowTreeHostWin::IsAnimatingClosed() const {
   return pending_close_;
 }
 
+bool DesktopWindowTreeHostWin::IsTranslucentWindowOpacitySupported() const {
+  return ui::win::IsAeroGlassEnabled();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopWindowTreeHostWin, WindowTreeHost implementation:
 
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_win.h b/ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
index 5fb0639..225365f 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
@@ -103,6 +103,7 @@ class VIEWS_EXPORT DesktopWindowTreeHostWin
   virtual void OnNativeWidgetFocus() OVERRIDE;
   virtual void OnNativeWidgetBlur() OVERRIDE;
   virtual bool IsAnimatingClosed() const OVERRIDE;
+  virtual bool IsTranslucentWindowOpacitySupported() const OVERRIDE;
 
   // Overridden from aura::WindowTreeHost:
   virtual ui::EventSource* GetEventSource() OVERRIDE;
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
index e7d86b5..74026c1 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
@@ -831,6 +831,10 @@ bool DesktopWindowTreeHostX11::IsAnimatingClosed() const {
   return false;
 }
 
+bool DesktopWindowTreeHostX11::IsTranslucentWindowOpacitySupported() const {
+  return false;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopWindowTreeHostX11, aura::WindowTreeHost implementation:
 
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
index cbcd9fc..cee65f5 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
@@ -144,6 +144,7 @@ class VIEWS_EXPORT DesktopWindowTreeHostX11
   virtual void OnNativeWidgetFocus() OVERRIDE;
   virtual void OnNativeWidgetBlur() OVERRIDE;
   virtual bool IsAnimatingClosed() const OVERRIDE;
+  virtual bool IsTranslucentWindowOpacitySupported() const OVERRIDE;
 
   // Overridden from aura::WindowTreeHost:
   virtual ui::EventSource* GetEventSource() OVERRIDE;
diff --git a/ui/views/widget/native_widget_aura.cc b/ui/views/widget/native_widget_aura.cc
index e26c52c..a1f05c4 100644
--- a/ui/views/widget/native_widget_aura.cc
+++ b/ui/views/widget/native_widget_aura.cc
@@ -691,6 +691,10 @@ ui::NativeTheme* NativeWidgetAura::GetNativeTheme() const {
 void NativeWidgetAura::OnRootViewLayout() const {
 }
 
+bool NativeWidgetAura::IsTranslucentWindowOpacitySupported() const {
+  return true;
+}
+
 void NativeWidgetAura::RepostNativeEvent(gfx::NativeEvent native_event) {
   OnEvent(native_event);
 }
diff --git a/ui/views/widget/native_widget_aura.h b/ui/views/widget/native_widget_aura.h
index 3b1e58a..dd6fafe 100644
--- a/ui/views/widget/native_widget_aura.h
+++ b/ui/views/widget/native_widget_aura.h
@@ -132,6 +132,7 @@ class VIEWS_EXPORT NativeWidgetAura
   virtual void SetVisibilityChangedAnimationsEnabled(bool value) OVERRIDE;
   virtual ui::NativeTheme* GetNativeTheme() const OVERRIDE;
   virtual void OnRootViewLayout() const OVERRIDE;
+  virtual bool IsTranslucentWindowOpacitySupported() const OVERRIDE;
   virtual void RepostNativeEvent(gfx::NativeEvent native_event) OVERRIDE;
 
   // Overridden from views::InputMethodDelegate:
diff --git a/ui/views/widget/native_widget_mac.h b/ui/views/widget/native_widget_mac.h
index 0cd87b7..64cb9a3 100644
--- a/ui/views/widget/native_widget_mac.h
+++ b/ui/views/widget/native_widget_mac.h
@@ -102,6 +102,7 @@ class VIEWS_EXPORT NativeWidgetMac : public internal::NativeWidgetPrivate {
   virtual void SetVisibilityChangedAnimationsEnabled(bool value) OVERRIDE;
   virtual ui::NativeTheme* GetNativeTheme() const OVERRIDE;
   virtual void OnRootViewLayout() const OVERRIDE;
+  virtual bool IsTranslucentWindowOpacitySupported() const OVERRIDE;
   virtual void RepostNativeEvent(gfx::NativeEvent native_event) OVERRIDE;
 
  private:
diff --git a/ui/views/widget/native_widget_mac.mm b/ui/views/widget/native_widget_mac.mm
index 729207a..37545b9 100644
--- a/ui/views/widget/native_widget_mac.mm
+++ b/ui/views/widget/native_widget_mac.mm
@@ -359,6 +359,10 @@ void NativeWidgetMac::OnRootViewLayout() const {
   NOTIMPLEMENTED();
 }
 
+bool NativeWidgetMac::IsTranslucentWindowOpacitySupported() const {
+  return false;
+}
+
 void NativeWidgetMac::RepostNativeEvent(gfx::NativeEvent native_event) {
   NOTIMPLEMENTED();
 }
diff --git a/ui/views/widget/native_widget_private.h b/ui/views/widget/native_widget_private.h
index d87bb0f..8c9233a 100644
--- a/ui/views/widget/native_widget_private.h
+++ b/ui/views/widget/native_widget_private.h
@@ -227,6 +227,7 @@ class VIEWS_EXPORT NativeWidgetPrivate : public NativeWidget {
   virtual void SetVisibilityChangedAnimationsEnabled(bool value) = 0;
   virtual ui::NativeTheme* GetNativeTheme() const = 0;
   virtual void OnRootViewLayout() const = 0;
+  virtual bool IsTranslucentWindowOpacitySupported() const = 0;
 
   // Repost an unhandled event to the native widget for default OS processing.
   virtual void RepostNativeEvent(gfx::NativeEvent native_event) = 0;
diff --git a/ui/views/widget/widget.cc b/ui/views/widget/widget.cc
index fdcb32a..3f4a170 100644
--- a/ui/views/widget/widget.cc
+++ b/ui/views/widget/widget.cc
@@ -981,6 +981,10 @@ void Widget::OnRootViewLayout() {
   native_widget_->OnRootViewLayout();
 }
 
+bool Widget::IsTranslucentWindowOpacitySupported() const {
+  return native_widget_->IsTranslucentWindowOpacitySupported();
+}
+
 void Widget::OnOwnerClosing() {
 }
 
diff --git a/ui/views/widget/widget.h b/ui/views/widget/widget.h
index bc3f914..c76633b 100644
--- a/ui/views/widget/widget.h
+++ b/ui/views/widget/widget.h
@@ -198,6 +198,9 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
     WidgetDelegate* delegate;
     bool child;
     // If TRANSLUCENT_WINDOW, the widget may be fully or partially transparent.
+    // Translucent windows may not always be supported. Use
+    // IsTranslucentWindowOpacitySupported to determine if translucent windows
+    // are supported.
     // If OPAQUE_WINDOW, we can perform optimizations based on the widget being
     // fully opaque.  Defaults to TRANSLUCENT_WINDOW if
     // ViewsDelegate::UseTransparentWindows().  Defaults to OPAQUE_WINDOW for
@@ -726,6 +729,9 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
   // window sizing information to the window server on some platforms.
   void OnRootViewLayout();
 
+  // Whether the widget supports translucency.
+  bool IsTranslucentWindowOpacitySupported() const;
+
   // Notification that our owner is closing.
   // NOTE: this is not invoked for aura as it's currently not needed there.
   // Under aura menus close by way of activation getting reset when the owner
diff --git a/ui/views/widget/widget_unittest.cc b/ui/views/widget/widget_unittest.cc
index d6ab099..d606206 100644
--- a/ui/views/widget/widget_unittest.cc
+++ b/ui/views/widget/widget_unittest.cc
@@ -623,6 +623,7 @@ class WidgetWithDestroyedNativeViewTest : public ViewsTestBase {
     widget->ReleaseCapture();
     widget->HasCapture();
     widget->GetWorkAreaBoundsInScreen();
+    widget->IsTranslucentWindowOpacitySupported();
   }
 
  private: