cc: Block commit on activate by setting a flag on LayerTreeHost.

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index 516fa69d213cdac607e610b2cd7427845049dbaf..7390a323cc116dc96375df781cdf2e809de7155d 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -244,6 +244,10 @@ void SingleThreadProxy::SetNeedsRedraw(gfx::Rect damage_rect) {
   SetNeedsRedrawRectOnImplThread(damage_rect);
 }
 
+void SingleThreadProxy::SetNextCommitWaitsForActivation() {
+  // There is no activation here other than commit. So do nothing.
+}
+
 void SingleThreadProxy::SetDeferCommits(bool defer_commits) {
   // Thread-only feature.
   NOTREACHED();