cc: Handle retroactive BeginFrames in the Scheduler.

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 69f42e00d8f08e66e4c888a6a8df9ef045d30ee1..ed8de3406c6c6eb514e237307904b38f1d12c80f 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -83,10 +83,9 @@ class LayerTreeHostImplForTesting : public LayerTreeHostImpl {
         block_notify_ready_to_activate_for_testing_(false),
         notify_ready_to_activate_was_blocked_(false) {}
 
-  virtual void BeginImplFrame(const BeginFrameArgs& args) OVERRIDE {
+  virtual void WillBeginImplFrame(const BeginFrameArgs& args) OVERRIDE {
+    LayerTreeHostImpl::WillBeginImplFrame(args);
     test_hooks_->WillBeginImplFrameOnThread(this, args);
-    LayerTreeHostImpl::BeginImplFrame(args);
-    test_hooks_->DidBeginImplFrameOnThread(this, args);
   }
 
   virtual void BeginMainFrameAborted(bool did_handle) OVERRIDE {
@@ -628,7 +627,7 @@ void LayerTreeTest::RunTest(bool threaded,
 
   delegating_renderer_ = delegating_renderer;
 
-  // Spend less time waiting for BeginImplFrame because the output is
+  // Spend less time waiting for BeginFrame because the output is
   // mocked out.
   settings_.refresh_rate = 200.0;
   if (impl_side_painting) {