[content] Fix background color update handling in RWHVAura.

content/browser/renderer_host/render_widget_host_view_mac.h

Index: content/browser/renderer_host/render_widget_host_view_mac.h
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.h b/content/browser/renderer_host/render_widget_host_view_mac.h
index 3395188313c87beea099e7e6bccffd511549acce..dc60660da1efaca18a12c53d4e4d171d2c0c43e2 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.h
+++ b/content/browser/renderer_host/render_widget_host_view_mac.h
@@ -277,6 +277,7 @@ class CONTENT_EXPORT RenderWidgetHostViewMac
   bool IsSpeaking() const override;
   void StopSpeaking() override;
   void SetBackgroundColor(SkColor color) override;
+  SkColor background_color() const override;
   void SetNeedsBeginFrames(bool needs_begin_frames) override;
 
   // Implementation of RenderWidgetHostViewBase.
@@ -565,6 +566,9 @@ class CONTENT_EXPORT RenderWidgetHostViewMac
   // The current selection range relative to the start of the web page.
   gfx::Range selection_range_;
 
+  // The background color of the widget.
+  SkColor background_color_;
+
   // Factory used to safely scope delayed calls to ShutdownHost().
   base::WeakPtrFactory<RenderWidgetHostViewMac> weak_factory_;