cc: Merge the DrawLayer()/DrawFrame() and SwapBuffers() methods.

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 8f82745bf326761992f34f2d70235a1289d29adb..c81549c54142451b4f60022c608a765e817f16cc 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -183,8 +183,8 @@ class LayerTreeHostImplForTesting : public LayerTreeHostImpl {
     return test_hooks_->PrepareToDrawOnThread(this, frame, draw_result);
   }
 
-  bool SwapBuffers(const FrameData& frame) override {
-    bool r = LayerTreeHostImpl::SwapBuffers(frame);
+  bool DrawLayers(FrameData* frame) override {
+    bool r = LayerTreeHostImpl::DrawLayers(frame);
     test_hooks_->DrawLayersOnThread(this);
     return r;
   }