[content] Fix background color update handling in RWHVAura.

content/browser/frame_host/render_widget_host_view_child_frame.h

Index: content/browser/frame_host/render_widget_host_view_child_frame.h
diff --git a/content/browser/frame_host/render_widget_host_view_child_frame.h b/content/browser/frame_host/render_widget_host_view_child_frame.h
index 3bf35d1b3053daba6f3307964ee72cae383f6888..cd57deb5642a38314fea6fc58bd1c675d82ec06c 100644
--- a/content/browser/frame_host/render_widget_host_view_child_frame.h
+++ b/content/browser/frame_host/render_widget_host_view_child_frame.h
@@ -85,6 +85,7 @@ class CONTENT_EXPORT RenderWidgetHostViewChildFrame
   gfx::NativeView GetNativeView() const override;
   gfx::NativeViewAccessible GetNativeViewAccessible() override;
   void SetBackgroundColor(SkColor color) override;
+  SkColor background_color() const override;
   gfx::Size GetPhysicalBackingSize() const override;
   bool IsMouseLocked() override;
   void SetNeedsBeginFrames(bool needs_begin_frames) override;
@@ -256,6 +257,9 @@ class CONTENT_EXPORT RenderWidgetHostViewChildFrame
   // The surface client ID of the parent RenderWidgetHostView.  0 if none.
   cc::FrameSinkId parent_frame_sink_id_;
 
+  // The background color of the widget.
+  SkColor background_color_;
+
   base::WeakPtrFactory<RenderWidgetHostViewChildFrame> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewChildFrame);
 };