Get rid of the remaining uses of GraphicsLayer.

sky/engine/platform/graphics/gpu/DrawingBuffer.cpp

Index: sky/engine/platform/graphics/gpu/DrawingBuffer.cpp
diff --git a/sky/engine/platform/graphics/gpu/DrawingBuffer.cpp b/sky/engine/platform/graphics/gpu/DrawingBuffer.cpp
index d65339d0f22f4a1be128f1ab4daac30309e72f38..cd505f6b0e370674671c99b3ed8f0e9c281cce68 100644
--- a/sky/engine/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/sky/engine/platform/graphics/gpu/DrawingBuffer.cpp
@@ -510,7 +510,6 @@ WebLayer* DrawingBuffer::platformLayer()
         m_layer->setOpaque(!m_actualAttributes.alpha);
         m_layer->setBlendBackgroundColor(m_actualAttributes.alpha);
         m_layer->setPremultipliedAlpha(m_actualAttributes.premultipliedAlpha);
-        GraphicsLayer::registerContentsLayer(m_layer->layer());
     }
 
     return m_layer->layer();
@@ -612,9 +611,6 @@ void DrawingBuffer::beginDestruction()
     m_multisampleFBO = 0;
     m_fbo = 0;
     m_contextEvictionManager.clear();
-
-    if (m_layer)
-        GraphicsLayer::unregisterContentsLayer(m_layer->layer());
 }
 
 unsigned DrawingBuffer::createColorTexture()