cc: Make LayerTreeHostImpl::SwapBuffers not virtual.

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 5666e12c84182855e52930111ea1e754b673cec3..c72d1f283d1a0299057328f1c9787dc075742244 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -242,15 +242,9 @@ class LayerTreeHostImplForTesting : public LayerTreeHostImpl {
     test_hooks_->DrawLayersOnThread(this);
   }
 
-  bool SwapBuffers(const LayerTreeHostImpl::FrameData& frame) override {
-    bool result = LayerTreeHostImpl::SwapBuffers(frame);
-    test_hooks_->SwapBuffersOnThread(this, result);
-    return result;
-  }
-
   void DidSwapBuffersComplete() override {
     LayerTreeHostImpl::DidSwapBuffersComplete();
-    test_hooks_->SwapBuffersCompleteOnThread(this);
+    test_hooks_->SwapBuffersCompleteOnThread();
   }
 
   void ReclaimResources(const CompositorFrameAck* ack) override {