Activate LayerImpl tree with sync+push instead of pointer swap

cc/solid_color_layer_impl.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_SOLID_COLOR_LAYER_IMPL_H_
 #define CC_SOLID_COLOR_LAYER_IMPL_H_
 
+#include "base/memory/scoped_ptr.h"
 #include "cc/cc_export.h"
 #include "cc/layer_impl.h"
 
 namespace cc {
 
 class CC_EXPORT SolidColorLayerImpl : public LayerImpl {
 public:
     static scoped_ptr<SolidColorLayerImpl> create(LayerTreeImpl* treeImpl, int id)
     {
         return make_scoped_ptr(new SolidColorLayerImpl(treeImpl, id));
     }
     virtual ~SolidColorLayerImpl();
 
+    // LayerImpl overrides.
+    virtual scoped_ptr<LayerImpl> createLayerImpl(LayerTreeImpl*) OVERRIDE;
     virtual void appendQuads(QuadSink&, AppendQuadsData&) OVERRIDE;
 
 protected:
     SolidColorLayerImpl(LayerTreeImpl* treeImpl, int id);
 
 private:
     virtual const char* layerTypeAsString() const OVERRIDE;
 
     const int m_tileSize;
 };
 
 }
 
 #endif  // CC_SOLID_COLOR_LAYER_IMPL_H_