Update scrollbar layer opacity when scrollbar theme changes

Source/platform/graphics/GraphicsLayer.cpp

 /*
  * Copyright (C) 2009 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 876 matching lines @@
 
     m_backgroundColor = color;
     m_layer->layer()->setBackgroundColor(m_backgroundColor.rgb());
 }
 
 void GraphicsLayer::setContentsOpaque(bool opaque)
 {
     m_contentsOpaque = opaque;
     m_layer->layer()->setOpaque(m_contentsOpaque);
     m_opaqueRectTrackingContentLayerDelegate->setOpaque(m_contentsOpaque);
+    if (m_contentsLayer)
+        m_contentsLayer->setOpaque(opaque);
 }
 
 void GraphicsLayer::setMaskLayer(GraphicsLayer* maskLayer)
 {
     if (maskLayer == m_maskLayer)
         return;
 
     m_maskLayer = maskLayer;
     WebLayer* maskWebLayer = m_maskLayer ? m_maskLayer->platformLayer() : 0;
     m_layer->layer()->setMaskLayer(maskWebLayer);
@@ skipping 220 matching lines @@
 #ifndef NDEBUG
 void showGraphicsLayerTree(const WebCore::GraphicsLayer* layer)
 {
     if (!layer)
         return;
 
     String output = layer->layerTreeAsText(WebCore::LayerTreeIncludesDebugInfo);
     fprintf(stderr, "%s\n", output.utf8().data());
 }
 #endif