cc: Plumbing for BeginFrameSource based on Surfaces

cc/surfaces/display_scheduler.cc

 // Copyright 2015 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/surfaces/display_scheduler.h"
 
 #include <vector>
 
 #include "base/stl_util.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 15 matching lines @@
       expecting_root_surface_damage_because_of_resize_(false),
       all_active_child_surfaces_ready_to_draw_(false),
       pending_swaps_(0),
       max_pending_swaps_(max_pending_swaps),
       root_surface_damaged_(false),
       expect_damage_from_root_surface_(false),
       weak_ptr_factory_(this) {
   begin_frame_source_->AddObserver(this);
   begin_frame_deadline_closure_ = base::Bind(
       &DisplayScheduler::OnBeginFrameDeadline, weak_ptr_factory_.GetWeakPtr());
+
+  // TODO(tansell): Set this to something useful.
+  begin_frame_source_for_children_ = SyntheticBeginFrameSource::Create(
+      task_runner, BeginFrameArgs::DefaultInterval());
 }
 
 DisplayScheduler::~DisplayScheduler() {
   begin_frame_source_->RemoveObserver(this);
 }
 
 // If we try to draw when the root surface resources are locked, the
 // draw will fail.
 void DisplayScheduler::SetRootSurfaceResourcesLocked(bool locked) {
   TRACE_EVENT1("cc", "DisplayScheduler::SetRootSurfaceResourcesLocked",
@@ skipping 239 matching lines @@
 }
 
 void DisplayScheduler::DidSwapBuffersComplete() {
   pending_swaps_--;
   TRACE_EVENT1("cc", "DisplayScheduler::DidSwapBuffersComplete",
                "pending_frames", pending_swaps_);
   ScheduleBeginFrameDeadline();
 }
 
 }  // namespace cc