cc: Introduce forward_begin_frames_to_children and use_external_begin_frame_source

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 <algorithm>
 #include <limits>
 
 #include "base/basictypes.h"
@@ skipping 2074 matching lines @@
     CreateAndSetTileManager();
 
   // Initialize vsync parameters to sane values.
   const base::TimeDelta display_refresh_interval =
       base::TimeDelta::FromMicroseconds(base::Time::kMicrosecondsPerSecond /
                                         settings_.refresh_rate);
   CommitVSyncParameters(base::TimeTicks(), display_refresh_interval);
 
   // TODO(brianderson): Don't use a hard-coded parent draw time.
   base::TimeDelta parent_draw_time =
-      (!settings_.begin_frame_scheduling_enabled &&
+      (!settings_.use_external_begin_frame_source &&
        output_surface_->capabilities().adjust_deadline_for_parent)
           ? BeginFrameArgs::DefaultEstimatedParentDrawTime()
           : base::TimeDelta();
   client_->SetEstimatedParentDrawTime(parent_draw_time);
 
   int max_frames_pending = output_surface_->capabilities().max_frames_pending;
   if (max_frames_pending <= 0)
     max_frames_pending = OutputSurface::DEFAULT_MAX_FRAMES_PENDING;
   client_->SetMaxSwapsPendingOnImplThread(max_frames_pending);
   client_->OnCanDrawStateChanged(CanDraw());
@@ skipping 1308 matching lines @@
 }
 
 void LayerTreeHostImpl::UnregisterPictureLayerImpl(PictureLayerImpl* layer) {
   std::vector<PictureLayerImpl*>::iterator it =
       std::find(picture_layers_.begin(), picture_layers_.end(), layer);
   DCHECK(it != picture_layers_.end());
   picture_layers_.erase(it);
 }
 
 }  // namespace cc