Add test for begin frames when using SingleThreadProxy.

cc/trees/layer_tree_host_unittest.cc

Index: cc/trees/layer_tree_host_unittest.cc
diff --git a/cc/trees/layer_tree_host_unittest.cc b/cc/trees/layer_tree_host_unittest.cc
index be879af1384d097e5b7d9ef53ec4ea1603c10248..95f9b753812bba6cdc6715c23cb16fd899087030 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -2776,6 +2776,39 @@ class LayerTreeHostTestAbortedCommitDoesntStallSynchronousCompositor
 MULTI_THREAD_TEST_F(
     LayerTreeHostTestAbortedCommitDoesntStallSynchronousCompositor);
 
+class LayerTreeHostTestBeginFrameNotificationSynchronousCompositor
+    : public LayerTreeHostTest {
+ protected:
+  void BeginTest() override {
+    saw_will_begin_impl_frame_ = false;
+    PostCompositeImmediatelyToMainThread();
+  }
+
+  void InitializeSettings(LayerTreeSettings* settings) override {
+    settings->using_synchronous_renderer_compositor = true;
+    settings->single_thread_proxy_scheduler = false;
+  }
+
+  void WillBeginImplFrameOnThread(LayerTreeHostImpl* impl,
+                                  const BeginFrameArgs& args) override {
+    EXPECT_EQ(base::TimeTicks(), args.deadline);
+    EXPECT_EQ(BeginFrameArgs::DefaultInterval(), args.interval);
+    saw_will_begin_impl_frame_ = true;

[enne (OOO), 2015/05/04 22:30:27]

I guess it was my understanding that it was also that BeginMainFrame happens
between this and DidBeginImplFrameDeadline?

+  }
+
+  void DidCommitAndDrawFrame() override { EndTest(); }
+
+  void AfterTest() override { EXPECT_TRUE(saw_will_begin_impl_frame_); }
+
+ private:
+  bool saw_will_begin_impl_frame_;
+};
+
+TEST_F(LayerTreeHostTestBeginFrameNotificationSynchronousCompositor,
+       BeginFrameReceived) {
+  RunTest(false, true, true);
+}
+
 class LayerTreeHostTestAbortedCommitDoesntStallDisabledVsync
     : public LayerTreeHostTestAbortedCommitDoesntStall {
   void InitializeSettings(LayerTreeSettings* settings) override {