Re-land "Drop background color optimization for composited layers"

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 81 matching lines @@
     , m_hasScrollParent(false)
     , m_hasClipParent(false)
     , m_paintingPhase(GraphicsLayerPaintAllWithOverflowClip)
     , m_contentsOrientation(CompositingCoordinatesTopDown)
     , m_parent(0)
     , m_maskLayer(0)
     , m_contentsClippingMaskLayer(0)
     , m_replicaLayer(0)
     , m_replicatedLayer(0)
     , m_paintCount(0)
-    , m_contentsSolidColor(Color::transparent)
     , m_contentsLayer(0)
     , m_contentsLayerId(0)
     , m_scrollableArea(0)
     , m_3dRenderingContext(0)
 {
 #ifndef NDEBUG
     if (m_client)
         m_client->verifyNotPainting();
 #endif
 
@@ skipping 906 matching lines @@
     RefPtr<NativeImageSkia> nativeImage = image ? image->nativeImageForCurrentFrame() : nullptr;
     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.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