Remove RenderWidget::SetBackground, change IPC to pass a bool.

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 1620e24fa52f75f4a1c34a46b906df859e01aea9..fff83a76f75e65de9d6bcc6775d56746fc5d07ac 100644
--- a/content/public/browser/render_widget_host_view.h
+++ b/content/public/browser/render_widget_host_view.h
@@ -102,9 +102,9 @@ class CONTENT_EXPORT RenderWidgetHostView {
   virtual base::string16 GetSelectedText() const = 0;
 
   // Subclasses should override this method to do what is appropriate to set
-  // the custom background for their platform.
-  virtual void SetBackground(const SkBitmap& background) = 0;
-  virtual const SkBitmap& GetBackground() = 0;
+  // the background to be transparent or opaque.
+  virtual void SetBackgroundOpaque(bool opaque) = 0;
+  virtual bool GetBackgroundOpaque() = 0;
 
   // Return value indicates whether the mouse is locked successfully or not.
   virtual bool LockMouse() = 0;