Transfer theme & page background colors between changes of RWHV.

content/public/browser/render_widget_host_view.h

Index: content/public/browser/render_widget_host_view.h
diff --git a/content/public/browser/render_widget_host_view.h b/content/public/browser/render_widget_host_view.h
index 36f7e78456573110a81cf847a04ca7d9869dd732..a17e4639f46ef8ba129d7449ba0436f18752495e 100644
--- a/content/public/browser/render_widget_host_view.h
+++ b/content/public/browser/render_widget_host_view.h
@@ -129,6 +129,8 @@ class CONTENT_EXPORT RenderWidgetHostView {
   // Subclasses should override this method to set the background color. |color|
   // could be transparent or opaque.
   virtual void SetBackgroundColor(SkColor color) = 0;
+  // Returns the background color set above.
+  virtual SkColor background_color() = 0;
   // Convenience method to fill the background layer with the default color by
   // calling |SetBackgroundColor|.
   virtual void SetBackgroundColorToDefault() = 0;