Re-enable solid background color optimization for composited layers.

Source/core/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 977 matching lines @@
     RefPtr<NativeImageSkia> nativeImage = image ? image->nativeImageForCurrentFrame() : 0;
     if (nativeImage) {
         m_ninePatchLayer = adoptPtr(Platform::current()->compositorSupport()->createNinePatchLayer());
         m_ninePatchLayer->setBitmap(nativeImage->bitmap(), aperture);
         m_ninePatchLayer->layer()->setOpaque(image->currentFrameKnownToBeOpaque());
         registerContentsLayer(m_ninePatchLayer->layer());
     }
     setContentsTo(m_ninePatchLayer ? m_ninePatchLayer->layer() : 0);
 }
 
+void GraphicsLayer::setContentsToSolidColor(const Color& color)
+{
+    if (color == m_contentsSolidColor)
+        return;
+
+    m_contentsSolidColor = color;
+    if (color.isValid() && color.alpha()) {
+        if (!m_solidColorLayer) {
+            m_solidColorLayer = adoptPtr(Platform::current()->compositorSupport()->createSolidColorLayer());
+            registerContentsLayer(m_solidColorLayer->layer());
+        }
+        m_solidColorLayer->setBackgroundColor(color.rgb());
+    } else {
+        if (!m_solidColorLayer)
+            return;
+        unregisterContentsLayer(m_solidColorLayer->layer());
+        m_solidColorLayer.clear();
+    }
+    setContentsTo(m_solidColorLayer ? m_solidColorLayer->layer() : 0);
+}
+
 bool GraphicsLayer::addAnimation(PassOwnPtr<WebAnimation> popAnimation)
 {
     OwnPtr<WebAnimation> animation(popAnimation);
     ASSERT(animation);
     platformLayer()->setAnimationDelegate(this);
 
     // Remove any existing animations with the same animation id and target property.
     platformLayer()->removeAnimation(animation->id(), animation->targetProperty());
     return platformLayer()->addAnimation(animation.leakPtr());
 }
@@ skipping 171 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