cc: Block the main thread for texture layers during impl-side painting

cc/thread_proxy.h

Index: cc/thread_proxy.h
diff --git a/cc/thread_proxy.h b/cc/thread_proxy.h
index 5320ee2accd79da56aca971ed7ce3838c101c8d8..cd7eaecbbc43a99f594bd67203f24cf7e539046c 100644
--- a/cc/thread_proxy.h
+++ b/cc/thread_proxy.h
@@ -134,6 +134,8 @@ private:
     void forceSerializeOnSwapBuffersOnImplThread(CompletionEvent*);
     void setNeedsForcedCommitOnImplThread();
     void commitPendingOnImplThreadForTesting(CommitPendingRequest* request);
+    void blockUntilPendingActivationIfNeeded();
+    void blockUntilPendingActivationOnImplThread(CompletionEvent*);
 
     // Accessed on main thread only.
     bool m_animateRequested; // Set only when setNeedsAnimate is called.
@@ -176,6 +178,9 @@ private:
     // Set when the main thread is waiting on layers to be drawn.
     CompletionEvent* m_textureAcquisitionCompletionEventOnImplThread;
 
+    // Set when the main thread is waiting for pending tree activation.
+    CompletionEvent* m_pendingTreeActivationEventOnImplThread;
+
     scoped_ptr<ResourceUpdateController> m_currentResourceUpdateControllerOnImplThread;
 
     // Set when the next draw should post didCommitAndDrawFrame to the main thread.