cc: Rename VSync to BeginFrame

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 95ee7b2e06ed0de6a0bb6940ba8131c7b153f658..028c5f46cfeb5be976d9fe7e4061a3e58650ec4b 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -221,9 +221,9 @@ class LayerTreeHostClientForTesting : public LayerTreeHostClient {
   }
   virtual ~LayerTreeHostClientForTesting() {}
 
-  virtual void WillBeginFrame() OVERRIDE {}
+  virtual void WillBeginMainFrame() OVERRIDE {}
 
-  virtual void DidBeginFrame() OVERRIDE {}
+  virtual void DidBeginMainFrame() OVERRIDE {}
 
   virtual void Animate(double monotonic_time) OVERRIDE {
     test_hooks_->Animate(base::TimeTicks::FromInternalValue(
@@ -548,7 +548,8 @@ void LayerTreeTest::RunTest(bool threaded,
 
   delegating_renderer_ = delegating_renderer;
 
-  // Spend less time waiting for vsync because the output is mocked out.
+  // Spend less time waiting for BeginImplFrame because the output is
+  // mocked out.
   settings_.refresh_rate = 200.0;
   if (impl_side_painting) {
     DCHECK(threaded) <<