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 3b0dd65d4c5e6a45f209fd5e5cedd34fb18f4924..ff659ae87a841e6d6814f44fed8820bbb2471d25 100644
--- a/content/public/browser/render_widget_host_view.h
+++ b/content/public/browser/render_widget_host_view.h
@@ -91,9 +91,9 @@ 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(const bool opaque) = 0;
+  virtual const bool GetBackgroundOpaque() = 0;
 
   // Return value indicates whether the mouse is locked successfully or not.
   virtual bool LockMouse() = 0;