cc/blimp: Add synchronization for scroll/scale state.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 5b90fd12c5a679f7c2823aa1327898fe84ed435e..d9f4f5208fb466f085275f533b21368d7a451ebb 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -338,6 +338,11 @@ void LayerTreeHostImpl::BeginCommit() {
 void LayerTreeHostImpl::CommitComplete() {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::CommitComplete");
 
+  // Apply any reflected deltas that were not applied during the main frame, if
+  // we use a pending tree.
+  if (!CommitToActiveTree())

[aelias_OOO_until_Jul13, 2016/10/26 04:04:12]

Can you DCHECK(!CommitToActiveTree()) inside the if
(reflected_main_frame_state_) {} block instead?

[Khushal, 2016/10/26 19:02:35]

I just DCHECKed !IsActiveTree() in that if block instead. That should be enough
right? Since in the CommitToActiveTree mode, there will be no pending tree.

+    sync_tree()->ApplyReflectedMainFrameState();
+
   if (CommitToActiveTree()) {
     // We have to activate animations here or "IsActive()" is true on the layers
     // but the animations aren't activated yet so they get ignored by