cc: Make separate interface for BeginFrame ipc from OutputSurface

cc/test/scheduler_test_common.h

Index: cc/test/scheduler_test_common.h
diff --git a/cc/test/scheduler_test_common.h b/cc/test/scheduler_test_common.h
index 2cb878acf5f66642da5ed34eadce0056968242a5..7c8fedb5a7ebfe6bf419dff14027835151ccea40 100644
--- a/cc/test/scheduler_test_common.h
+++ b/cc/test/scheduler_test_common.h
@@ -161,7 +161,8 @@ class TestScheduler : public Scheduler {
       scoped_refptr<TestNowSource> now_src,
       SchedulerClient* client,
       const SchedulerSettings& scheduler_settings,
-      int layer_tree_host_id) {
+      int layer_tree_host_id,
+      scoped_refptr<ExternalBeginFrameSource> external_begin_frame_source) {
     // A bunch of tests require Now() to be > BeginFrameArgs::DefaultInterval()
     now_src->AdvanceNow(base::TimeDelta::FromMilliseconds(100));
 
@@ -169,12 +170,15 @@ class TestScheduler : public Scheduler {
         new OrderedSimpleTaskRunner(now_src, true);
     TestSchedulerFrameSourcesConstructor frame_sources_constructor(
         test_task_runner.get(), now_src.get());
+    if (scheduler_settings.begin_frame_scheduling_enabled)
+      DCHECK(external_begin_frame_source.get());
     return make_scoped_ptr(new TestScheduler(now_src,
                                              client,
                                              scheduler_settings,
                                              layer_tree_host_id,
                                              test_task_runner,
-                                             &frame_sources_constructor));
+                                             &frame_sources_constructor,
+                                             external_begin_frame_source));
   }
 
   // Extra test helper functionality
@@ -182,6 +186,10 @@ class TestScheduler : public Scheduler {
     return begin_retro_frame_args_.empty();
   }
 
+  bool NeedsBeginFrames() const {
+    return primary_frame_source_->NeedsBeginFrames();
+  }
+
   BeginFrameSource& frame_source() { return *frame_source_; }
   OrderedSimpleTaskRunner& task_runner() { return *test_task_runner_; }
 
@@ -198,7 +206,8 @@ class TestScheduler : public Scheduler {
       const SchedulerSettings& scheduler_settings,
       int layer_tree_host_id,
       const scoped_refptr<OrderedSimpleTaskRunner>& test_task_runner,
-      TestSchedulerFrameSourcesConstructor* frame_sources_constructor);
+      TestSchedulerFrameSourcesConstructor* frame_sources_constructor,
+      scoped_refptr<ExternalBeginFrameSource> external_begin_frame_source);
 
   scoped_refptr<TestNowSource> now_src_;
   OrderedSimpleTaskRunner* test_task_runner_;