cc: Don't do full tree sync unless needed with impl painting.

cc/layer_tree_host_impl.h

 // Copyright 2011 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_TREE_HOST_IMPL_H_
 #define CC_LAYER_TREE_HOST_IMPL_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time.h"
@@ skipping 155 matching lines @@
 
     LayerTreeImpl* activeTree() { return m_activeTree.get(); }
     const LayerTreeImpl* activeTree() const { return m_activeTree.get(); }
     LayerTreeImpl* pendingTree() { return m_pendingTree.get(); }
     const LayerTreeImpl* pendingTree() const { return m_pendingTree.get(); }
     const LayerTreeImpl* recycleTree() const { return m_recycleTree.get(); }
     void createPendingTree();
     void checkForCompletedTileUploads();
     scoped_ptr<base::Value> activationStateAsValue() const;
     virtual void activatePendingTreeIfNeeded();
+    void setNeedsFullTreeSync(bool needs) { m_needsFullTreeSync = needs; }
 
     // Shortcuts to layers on the active tree.
     LayerImpl* rootLayer() const;
     LayerImpl* rootScrollLayer() const;
     LayerImpl* currentlyScrollingLayer() const;
 
     bool visible() const { return m_visible; }
     void setVisible(bool);
 
     size_t memoryAllocationLimitBytes() const { return m_managedMemoryPolicy.bytesLimitWhenVisible; }
@@ skipping 127 matching lines @@
     scoped_ptr<LayerTreeImpl> m_activeTree;
 
     // In impl-side painting mode, tree with possibly incomplete rasterized
     // content. May be promoted to active by activatePendingTreeIfNeeded().
     scoped_ptr<LayerTreeImpl> m_pendingTree;
 
     // In impl-side painting mode, inert tree with layers that can be recycled
     // by the next sync from the main thread.
     scoped_ptr<LayerTreeImpl> m_recycleTree;
 
+    // In impl-side painting mode, this is true when the main thread tree
+    // required a full sync into the pending tree, and so the structure of the
+    // pending tree may no longer match the structure of the active tree. A
+    // full sync should be used when activating the pending tree.
+    bool m_needsFullTreeSync;
+
     bool m_scrollDeltaIsInViewportSpace;
     LayerTreeSettings m_settings;
     LayerTreeDebugState m_debugState;
     gfx::Size m_layoutViewportSize;
     gfx::Size m_deviceViewportSize;
     float m_deviceScaleFactor;
     bool m_visible;
     ManagedMemoryPolicy m_managedMemoryPolicy;
 
     bool m_pinchGestureActive;
@@ skipping 24 matching lines @@
     base::TimeTicks m_currentFrameTime;
 
     scoped_ptr<AnimationRegistrar> m_animationRegistrar;
 
     DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYER_TREE_HOST_IMPL_H_