cc: Fix thread race on writing commit_waits_for_activation_.

cc/trees/thread_proxy.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/thread_proxy.h"
 
 #include <string>
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
@@ skipping 993 matching lines @@
 
   if (did_handle)
     SetInputThrottledUntilCommitOnImplThread(false);
   layer_tree_host_impl_->BeginMainFrameAborted(did_handle);
   scheduler_on_impl_thread_->BeginMainFrameAborted(did_handle);
 }
 
 void ThreadProxy::ScheduledActionCommit() {
   TRACE_EVENT0("cc", "ThreadProxy::ScheduledActionCommit");
   DCHECK(IsImplThread());
+  DCHECK(IsMainThreadBlocked());
   DCHECK(commit_completion_event_on_impl_thread_);
   DCHECK(current_resource_update_controller_on_impl_thread_);
 
   // Complete all remaining texture updates.
   current_resource_update_controller_on_impl_thread_->Finalize();
   current_resource_update_controller_on_impl_thread_.reset();
 
   inside_commit_ = true;
   layer_tree_host_impl_->BeginCommit();
   layer_tree_host()->BeginCommitOnImplThread(layer_tree_host_impl_.get());
   layer_tree_host()->FinishCommitOnImplThread(layer_tree_host_impl_.get());
   layer_tree_host_impl_->CommitComplete();
   inside_commit_ = false;
 
   SetInputThrottledUntilCommitOnImplThread(false);
 
   UpdateBackgroundAnimateTicking();
 
   next_frame_is_newly_committed_frame_on_impl_thread_ = true;
 
-  if (layer_tree_host()->settings().impl_side_painting &&
-      commit_waits_for_activation_) {
+  bool hold_commit = layer_tree_host()->settings().impl_side_painting &&
+                     commit_waits_for_activation_;
+  commit_waits_for_activation_ = false;
+
+  if (hold_commit) {
     // For some layer types in impl-side painting, the commit is held until
     // the pending tree is activated.  It's also possible that the
     // pending tree has already activated if there was no work to be done.
     TRACE_EVENT_INSTANT0("cc", "HoldCommit", TRACE_EVENT_SCOPE_THREAD);
     completion_event_for_commit_held_on_tree_activation_ =
         commit_completion_event_on_impl_thread_;
     commit_completion_event_on_impl_thread_ = NULL;
   } else {
     commit_completion_event_on_impl_thread_->Signal();
     commit_completion_event_on_impl_thread_ = NULL;
   }
 
-  commit_waits_for_activation_ = false;
-
   commit_complete_time_ = base::TimeTicks::HighResNow();
   begin_main_frame_to_commit_duration_history_.InsertSample(
       commit_complete_time_ - begin_main_frame_sent_time_);
 
   // SetVisible kicks off the next scheduler action, so this must be last.
   scheduler_on_impl_thread_->SetVisible(layer_tree_host_impl_->visible());
 }
 
 void ThreadProxy::ScheduledActionUpdateVisibleTiles() {
   DCHECK(IsImplThread());
@@ skipping 586 matching lines @@
   commit_to_activate_duration_history_.InsertSample(
       base::TimeTicks::HighResNow() - commit_complete_time_);
 }
 
 void ThreadProxy::DidManageTiles() {
   DCHECK(IsImplThread());
   scheduler_on_impl_thread_->DidManageTiles();
 }
 
 }  // namespace cc