Activate LayerImpl tree with sync+push instead of pointer swap

cc/layer_tree_impl.h

Index: cc/layer_tree_impl.h
diff --git a/cc/layer_tree_impl.h b/cc/layer_tree_impl.h
index bae0cb961ed6938e82f86391108a0f80f1b77152..8c7fd9d60ef3d92e399fe7aeefb08a6e76bbbd8d 100644
--- a/cc/layer_tree_impl.h
+++ b/cc/layer_tree_impl.h
@@ -55,6 +55,7 @@ class CC_EXPORT LayerTreeImpl {
   PaintTimeCounter* paint_time_counter() const;
   bool IsActiveTree() const;
   bool IsPendingTree() const;
+  bool IsRecycleTree() const;
   LayerImpl* FindActiveTreeLayerById(int id);
   LayerImpl* FindPendingTreeLayerById(int id);
   int MaxTextureSize() const;
@@ -139,6 +140,9 @@ class CC_EXPORT LayerTreeImpl {
   void SetContentsTexturesPurged();
   void ResetContentsTexturesPurged();
 
+  // Useful for debug assertions, probably shouldn't be used for anything else.
+  Proxy* proxy() const;
+
 protected:
   LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl);