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

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 320 matching lines @@
   if (compositor_frame_sink_)
     compositor_frame_sink_->ForceReclaimResources();
 
   if (!CommitToActiveTree())
     CreatePendingTree();
 }
 
 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
     // UpdateDrawProperties.
     ActivateAnimations();
   }
 
   // Start animations before UpdateDrawProperties and PrepareTiles, as they can
   // change the results. When doing commit to the active tree, this must happen
   // after ActivateAnimations() in order for this ticking to be propogated to
@@ skipping 3733 matching lines @@
   if (is_visible) {
     worker_context_visibility_ =
         worker_context->CacheController()->ClientBecameVisible();
   } else {
     worker_context->CacheController()->ClientBecameNotVisible(
         std::move(worker_context_visibility_));
   }
 }
 
 }  // namespace cc