cc: Introduce forward_begin_frames_to_children and use_external_begin_frame_source

cc/scheduler/scheduler.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/scheduler/scheduler.h"
 
 #include <algorithm>
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
@@ skipping 11 matching lines @@
     Scheduler* scheduler) {
   if (!scheduler->settings_.throttle_frame_production) {
     TRACE_EVENT1("cc",
                  "Scheduler::Scheduler()",
                  "PrimaryFrameSource",
                  "BackToBackBeginFrameSource");
     DCHECK(!scheduler->primary_frame_source_internal_);
     scheduler->primary_frame_source_internal_ =
         BackToBackBeginFrameSource::Create(scheduler->task_runner_.get());
     return scheduler->primary_frame_source_internal_.get();
-  } else if (scheduler->settings_.begin_frame_scheduling_enabled) {
+  } else if (scheduler->settings_.begin_frame_receiver) {
     TRACE_EVENT1("cc",
                  "Scheduler::Scheduler()",
                  "PrimaryFrameSource",
                  "ExternalBeginFrameSource");
     DCHECK(scheduler->primary_frame_source_internal_.get())
         << "Need external BeginFrameSource";
     return scheduler->primary_frame_source_internal_.get();
   } else {
     TRACE_EVENT1("cc",
                  "Scheduler::Scheduler()",
@@ skipping 736 matching lines @@
 }
 
 bool Scheduler::IsBeginMainFrameSentOrStarted() const {
   return (state_machine_.commit_state() ==
               SchedulerStateMachine::COMMIT_STATE_BEGIN_MAIN_FRAME_SENT ||
           state_machine_.commit_state() ==
               SchedulerStateMachine::COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED);
 }
 
 }  // namespace cc