cc: Send all begin frames using a PostTask.

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 c16eb978eaffc19d156f94b8522662f902b60187..6cba812e485c4138c5285e704c5cbadd91f05418 100644
--- a/cc/scheduler/scheduler_unittest.cc
+++ b/cc/scheduler/scheduler_unittest.cc
@@ -220,7 +220,7 @@ class SchedulerTest : public testing::Test {
   SchedulerTest()
       : now_src_(new base::SimpleTestTickClock()),
         task_runner_(new OrderedSimpleTaskRunner(now_src_.get(), true)),
-        fake_external_begin_frame_source_(nullptr) {
+        fake_compositor_timing_history_(nullptr) {
     now_src_->Advance(base::TimeDelta::FromMicroseconds(10000));
     // A bunch of tests require NowTicks()
     // to be > BeginFrameArgs::DefaultInterval()
@@ -234,15 +234,13 @@ class SchedulerTest : public testing::Test {
  protected:
   TestScheduler* CreateScheduler() {
     BeginFrameSource* frame_source;
-    unthrottled_frame_source_.reset(new BackToBackBeginFrameSource(
-        base::MakeUnique<TestDelayBasedTimeSource>(now_src_.get(),
-                                                   task_runner_.get())));
+    unthrottled_frame_source_.reset(
+        new BackToBackBeginFrameSource(task_runner_.get(), now_src_.get()));
     fake_external_begin_frame_source_.reset(
         new FakeExternalBeginFrameSource(0.f, false));
     fake_external_begin_frame_source_->SetClient(client_.get());
-    synthetic_frame_source_.reset(new DelayBasedBeginFrameSource(
-        base::MakeUnique<TestDelayBasedTimeSource>(now_src_.get(),
-                                                   task_runner_.get())));
+    synthetic_frame_source_.reset(
+        new DelayBasedBeginFrameSource(task_runner_.get(), now_src_.get()));
     if (!scheduler_settings_.throttle_frame_production) {
       frame_source = unthrottled_frame_source_.get();
     } else if (scheduler_settings_.use_external_begin_frame_source) {