Merge 122791 - [chromium] Turn off ScrollbarLayerChromium for Windows due to bad alpha values

Source/WebCore/page/scrolling/chromium/ScrollingCoordinatorChromium.cpp

 /*
  * Copyright (C) 2012 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 102 matching lines @@
         scrollLayer = scrollLayerForFrameView(frameView)->platformLayer();
         ASSERT(scrollLayer);
     }
 
     // Root layer non-overlay scrollbars should be marked opaque to disable
     // blending.
     bool isOpaqueRootScrollbar = !frameView->parent() && !scrollbar->isOverlayScrollbar();
     if (!scrollbarGraphicsLayer->contentsOpaque())
         scrollbarGraphicsLayer->setContentsOpaque(isOpaqueRootScrollbar);
 
-    // FIXME: Mac scrollbar themes are not thread-safe.
+    // FIXME: Mac scrollbar themes are not thread-safe to paint.
+    // FIXME: Win scrollbars on XP Classic themes do not paint valid alpha
+    // values due to GDI. This needs to be fixed in theme code before it
+    // can be turned on here.
     bool platformSupported = true;
-#if OS(DARWIN)
+#if OS(DARWIN) || OS(WINDOWS)
     platformSupported = false;
 #endif
 
     if (!platformSupported || scrollbar->isOverlayScrollbar()) {
         scrollbarGraphicsLayer->setContentsToMedia(0);
         scrollbarGraphicsLayer->setDrawsContent(true);
         return 0;
     }
 
     RefPtr<ScrollbarLayerChromium> scrollbarLayer = ScrollbarLayerChromium::create(scrollbar, scrollLayer->id());
@@ skipping 59 matching lines @@
         platformLayer->setIsContainerForFixedPositionLayers(enable);
 }
 
 void ScrollingCoordinator::setLayerIsFixedToContainerLayer(GraphicsLayer* layer, bool enable)
 {
     if (LayerChromium* platformLayer = layer->platformLayer())
         platformLayer->setFixedToContainerLayer(enable);
 }
 
 }