Create a new action triggered when a BeginMainFrame is not expected before vsync

cc/test/layer_tree_test.cc

Index: cc/test/layer_tree_test.cc
diff --git a/cc/test/layer_tree_test.cc b/cc/test/layer_tree_test.cc
index f5d9ee63ee551309de11dfc6e7045e38564d6695..9767ed7f5807fbc85091062cfef82d40ab0e21a3 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -354,6 +354,9 @@ class LayerTreeHostClientForTesting : public LayerTreeHostClient,
   void BeginMainFrameNotExpectedSoon() override {
     test_hooks_->BeginMainFrameNotExpectedSoon();
   }
+  void DoShortIdleWork(const BeginFrameArgs& args) override {
+    // TODO(delphick): do something here?

[Sami, 2017/03/24 15:24:11]

Unless we're testing something at this level this can just be blank.

[Dan Elphick, 2017/03/29 16:02:44]

Yeah it was just a reminder to check if we needed a test here since
BeginMainFrameNotExpectedSoon has hooks here. For now I'll remove it.

+  }
 
  private:
   explicit LayerTreeHostClientForTesting(TestHooks* test_hooks)