cc: Make separate interface for BeginFrame ipc from OutputSurface

cc/scheduler/scheduler_unittest.cc

Index: cc/scheduler/scheduler_unittest.cc
diff --git a/cc/scheduler/scheduler_unittest.cc b/cc/scheduler/scheduler_unittest.cc
index 9c459b5b0be6286cc7dc4fe017aaf08f32e5a7b2..88b803407f8dad4850423bccc2b1232e7afe9b56 100644
--- a/cc/scheduler/scheduler_unittest.cc
+++ b/cc/scheduler/scheduler_unittest.cc
@@ -81,8 +81,13 @@ class FakeSchedulerClient : public SchedulerClient {
     log_anticipated_draw_time_change_ = false;
   }
 
-  TestScheduler* CreateScheduler(const SchedulerSettings& settings) {
-    scheduler_ = TestScheduler::Create(now_src_, this, settings, 0);
+  TestScheduler* CreateScheduler(const SchedulerSettings& settings,
+                                 bool use_external_begin_frame_source) {
+    scheduler_ = TestScheduler::Create(now_src_,
+                                       this,
+                                       settings,
+                                       0,
+                                       use_external_begin_frame_source);
     DCHECK(scheduler_);
     // Fail if we need to run 100 tasks in a row.
     task_runner().SetRunTaskLimit(100);
@@ -107,14 +112,10 @@ class FakeSchedulerClient : public SchedulerClient {
     return scheduler_->settings().begin_frame_scheduling_enabled &&
            scheduler_->settings().throttle_frame_production;
   }
-  virtual FakeBeginFrameSource* ExternalBeginFrameSource() override {
-    return &fake_frame_source_;
-  }
 
   void AdvanceFrame() {
     TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler.frames"),
                  "FakeSchedulerClient::AdvanceFrame");
-    // EXPECT_TRUE(needs_begin_frames());
     if (ExternalBeginFrame()) {
       // Creep the time forward so that any BeginFrameArgs is not equal to the
       // last one otherwise we violate the BeginFrameSource contract.