[blink] Support (semi-)transparent background colors in WebView/Frame.

third_party/WebKit/public/platform/WebLayerTreeView.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 53 matching lines @@
 
   // Viewport size is given in physical pixels.
   virtual void setViewportSize(const WebSize& deviceViewportSize) {}
   virtual WebSize getViewportSize() const { return WebSize(); }
 
   virtual void setDeviceScaleFactor(float) {}
 
   // Sets the background color for the viewport.
   virtual void setBackgroundColor(WebColor) {}
 
-  // Sets the background transparency for the viewport. The default is 'false'.
-  virtual void setHasTransparentBackground(bool) {}
-
   // Sets whether this view is visible. In threaded mode, a view that is not
   // visible will not composite or trigger updateAnimations() or layout() calls
   // until it becomes visible.
   virtual void setVisible(bool) {}
 
   // Sets the current page scale factor and minimum / maximum limits. Both
   // limits are initially 1 (no page scale allowed).
   virtual void setPageScaleFactorAndLimits(float pageScaleFactor,
                                            float minimum,
                                            float maximum) {}
@@ skipping 98 matching lines @@
   // Toggles the debug borders on layers
   virtual void setShowDebugBorders(bool) {}
 
   // Toggles scroll bottleneck rects on the HUD layer
   virtual void setShowScrollBottleneckRects(bool) {}
 };
 
 }  // namespace blink
 
 #endif  // WebLayerTreeView_h