Only do full tree sync if tree is actually changed, otherwise just push properties

cc/layer_tree_host.h

Index: cc/layer_tree_host.h
diff --git a/cc/layer_tree_host.h b/cc/layer_tree_host.h
index fd73692038c455b5d720520b99afa4ac2c438c72..8f3087ce6f2fe7182468084cebd29e4ad2e1ce8c 100644
--- a/cc/layer_tree_host.h
+++ b/cc/layer_tree_host.h
@@ -184,6 +184,7 @@ public:
     void setNeedsAnimate();
     // virtual for testing
     virtual void setNeedsCommit();
+    virtual void setNeedsFullTreeSync();
     void setNeedsRedraw();
     bool commitRequested() const;
 
@@ -268,6 +269,7 @@ private:
 
     bool m_animating;
     bool m_needsAnimateLayers;
+    bool m_needsFullTreeSync;
 
     base::CancelableClosure m_prepaintCallback;