cc: Toward merging DrawFrame and SwapBuffers in DelegatingRenderer.

cc/output/delegating_renderer_unittest.cc

Index: cc/output/delegating_renderer_unittest.cc
diff --git a/cc/output/delegating_renderer_unittest.cc b/cc/output/delegating_renderer_unittest.cc
index 87fd7b6db8dd8021063ed55d9709ff24d92e6cb3..56451a7f91c0dc91df86a617d4671ef911cc909f 100644
--- a/cc/output/delegating_renderer_unittest.cc
+++ b/cc/output/delegating_renderer_unittest.cc
@@ -24,9 +24,12 @@ class DelegatingRendererTestDraw : public DelegatingRendererTest {
 
   void AfterTest() override {}
 
-  void DrawLayersOnThread(LayerTreeHostImpl* host_impl) override {
+  DrawResult PrepareToDrawOnThread(LayerTreeHostImpl* host_impl,
+                                   LayerTreeHostImpl::FrameData* frame_data,
+                                   DrawResult draw_result) override {
     EXPECT_EQ(0, num_swaps_);
     drawn_viewport_ = host_impl->DeviceViewport();
+    return draw_result;

[enne (OOO), 2016/09/07 18:05:51]

Previously this wouldn't have been called if the DrawResult was that it wasn't
going to draw? Maybe you should DCHECK draw result?

Or maybe drawn_viewport_ means something else here other than actually drawn?

[danakj, 2016/09/07 18:42:15]

Um, well, its the size of the viewport we're drawing this frame. I can dcheck
the draw result sure.

[danakj, 2016/09/07 18:52:00]

Done.

   }
 
   void DisplayReceivedCompositorFrameOnThread(