cc: Unify use of DidSwapBuffers() and did_request_swap

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index aa8addc31984872b8f00f2573bd0566517b9d03d..7b6fe8130dd5f87a799bd4235d43c75f6cab2a36 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -184,9 +184,8 @@ class CC_EXPORT LayerTreeHostImpl
   // to avoid displaying the frame. If PrepareToDraw is called, DidDrawAllLayers
   // must also be called, regardless of whether DrawLayers is called between the
   // two.
-  virtual DrawSwapReadbackResult::DrawResult PrepareToDraw(
-      FrameData* frame,
-      const gfx::Rect& damage_rect);
+  virtual DrawResult PrepareToDraw(FrameData* frame,
+                                   const gfx::Rect& damage_rect);
   virtual void DrawLayers(FrameData* frame, base::TimeTicks frame_begin_time);
   // Must be called if and only if PrepareToDraw was called.
   void DidDrawAllLayers(const FrameData& frame);
@@ -493,7 +492,7 @@ class CC_EXPORT LayerTreeHostImpl
   // This function should only be called from PrepareToDraw, as DidDrawAllLayers
   // must be called if this helper function is called.  Returns DRAW_SUCCESS if
   // the frame should be drawn.
-  DrawSwapReadbackResult::DrawResult CalculateRenderPasses(FrameData* frame);
+  DrawResult CalculateRenderPasses(FrameData* frame);
 
   void SendReleaseResourcesRecursive(LayerImpl* current);
   bool EnsureRenderSurfaceLayerList();