Retain references to surfaces from both active AND pending CompositorFrames

cc/surfaces/compositor_frame_sink_support.h

Index: cc/surfaces/compositor_frame_sink_support.h
diff --git a/cc/surfaces/compositor_frame_sink_support.h b/cc/surfaces/compositor_frame_sink_support.h
index cfdd0a2539f4827ed51b505cdab76feaf74b06b8..d0c8b169a334da9dbb1c7ccb83100a9328fdaa20 100644
--- a/cc/surfaces/compositor_frame_sink_support.h
+++ b/cc/surfaces/compositor_frame_sink_support.h
@@ -46,6 +46,10 @@ class CC_SURFACES_EXPORT CompositorFrameSinkSupport
     return surface_factory_.current_surface_for_testing();
   }
 
+  const ReferencedSurfaceTracker& reference_tracker_for_testing() const {

[vmpstr, 2017/02/10 00:24:40]

just as a style thing (sorry I missed it in the previous review), I think we
prefer ReferenceTrackerForTesting[1] (and in general that for ForTesting)
functions, and could you put them at the end of the public section with "// For
testing functions." comment for the block.

[1]:
cc$ git gs 'for_testing(' | wc -l
301
cc$ git gs 'ForTesting(' | wc -l
1702

[Fady Samuel, 2017/02/10 00:55:30]

Done.

+    return reference_tracker_;
+  }
+
   void EvictFrame();
   void SetNeedsBeginFrame(bool needs_begin_frame);
   void SubmitCompositorFrame(const LocalSurfaceId& local_surface_id,