Activate LayerImpl tree with sync+push instead of pointer swap

cc/layer.h

 // Copyright 2010 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_LAYER_H_
 #define CC_LAYER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 49 matching lines @@
     Layer* parent() { return m_parent; }
     const Layer* parent() const { return m_parent; }
     void addChild(scoped_refptr<Layer>);
     void insertChild(scoped_refptr<Layer>, size_t index);
     void replaceChild(Layer* reference, scoped_refptr<Layer> newLayer);
     void removeFromParent();
     void removeAllChildren();
     void setChildren(const LayerList&);
 
     const LayerList& children() const { return m_children; }
+    Layer* childAt(size_t index);
 
     void setAnchorPoint(const gfx::PointF&);
     gfx::PointF anchorPoint() const { return m_anchorPoint; }
 
     void setAnchorPointZ(float);
     float anchorPointZ() const { return m_anchorPointZ; }
 
     virtual void setBackgroundColor(SkColor);
     SkColor backgroundColor() const { return m_backgroundColor; }
 
@@ skipping 204 matching lines @@
 
     // In impl-side painting, this returns true if this layer type is not
     // compatible with the main thread running freely, such as a double-buffered
     // canvas that doesn't want to be triple-buffered across all three trees.
     virtual bool blocksPendingCommit() const;
     // Returns true if anything in this tree blocksPendingCommit.
     bool blocksPendingCommitRecursive() const;
 
     virtual bool canClipSelf() const;
 
+    // Constructs a LayerImpl of the correct runtime type for this Layer type.
+    virtual scoped_ptr<LayerImpl> createLayerImpl(LayerTreeImpl* treeImpl);
+
 protected:
     friend class LayerImpl;
     friend class TreeSynchronizer;
     virtual ~Layer();
 
     Layer();
 
     void setNeedsCommit();
     void setNeedsFullTreeSync();
 
     // This flag is set when layer need repainting/updating.
     bool m_needsDisplay;
 
     // Tracks whether this layer may have changed stacking order with its siblings.
     bool m_stackingOrderChanged;
 
     // The update rect is the region of the compositor resource that was actually updated by the compositor.
     // For layers that may do updating outside the compositor's control (i.e. plugin layers), this information
     // is not available and the update rect will remain empty.
     // Note this rect is in layer space (not content space).
     gfx::RectF m_updateRect;
 
     scoped_refptr<Layer> m_maskLayer;
 
-    // Constructs a LayerImpl of the correct runtime type for this Layer type.
-    virtual scoped_ptr<LayerImpl> createLayerImpl(LayerTreeImpl* treeImpl);
     int m_layerId;
 
     // When true, the layer is about to perform an update. Any commit requests
     // will be handled implcitly after the update completes.
     bool m_ignoreSetNeedsCommit;
 
 private:
     friend class base::RefCounted<Layer>;
 
     void setParent(Layer*);
@@ skipping 72 matching lines @@
     WebKit::WebLayerScrollClient* m_layerScrollClient;
 
     DrawProperties<Layer, RenderSurface> m_drawProperties;
 };
 
 void sortLayers(std::vector<scoped_refptr<Layer> >::iterator, std::vector<scoped_refptr<Layer> >::iterator, void*);
 
 }  // namespace cc
 
 #endif  // CC_LAYER_H_