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..59455000ee84bd17e30bb4942d5d505a2318cde9 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,
+      bool use_external_begin_frame_source) {
     // A bunch of tests require Now() to be > BeginFrameArgs::DefaultInterval()
     now_src->AdvanceNow(base::TimeDelta::FromMilliseconds(100));
 
@@ -169,12 +170,19 @@ class TestScheduler : public Scheduler {
         new OrderedSimpleTaskRunner(now_src, true);
     TestSchedulerFrameSourcesConstructor frame_sources_constructor(
         test_task_runner.get(), now_src.get());
-    return make_scoped_ptr(new TestScheduler(now_src,
-                                             client,
-                                             scheduler_settings,
-                                             layer_tree_host_id,
-                                             test_task_runner,
-                                             &frame_sources_constructor));
+    scoped_ptr<ExternalBeginFrameSource> external_begin_frame_source;
+    if (use_external_begin_frame_source) {
+      DCHECK(scheduler_settings.begin_frame_scheduling_enabled);
+      external_begin_frame_source.reset(new TestExternalBeginFrameSource);
+    }
+    return make_scoped_ptr(new TestScheduler(
+                                   now_src,
+                                   client,
+                                   scheduler_settings,
+                                   layer_tree_host_id,
+                                   test_task_runner,
+                                   &frame_sources_constructor,
+                                   external_begin_frame_source.Pass()));
   }
 
   // Extra test helper functionality
@@ -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_ptr<ExternalBeginFrameSource> external_begin_frame_source);
 
   scoped_refptr<TestNowSource> now_src_;
   OrderedSimpleTaskRunner* test_task_runner_;