Retain references to surfaces from both active AND pending CompositorFrames

cc/surfaces/compositor_frame_sink_support.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_SURFACES_COMPOSITOR_FRAME_SINK_SUPPORT_H_
 #define CC_SURFACES_COMPOSITOR_FRAME_SINK_SUPPORT_H_
 
 #include <memory>
 #include <unordered_set>
 
@@ skipping 28 matching lines @@
       std::unique_ptr<BeginFrameSource> display_begin_frame_source);
 
   ~CompositorFrameSinkSupport() override;
 
   const FrameSinkId& frame_sink_id() const { return frame_sink_id_; }
 
   Surface* current_surface_for_testing() {
     return surface_factory_.current_surface_for_testing();
   }
 
+  const ReferencedSurfaceTracker& ReferenceTrackerForTesting() const {
+    return reference_tracker_;
+  }
+
   void EvictFrame();
   void SetNeedsBeginFrame(bool needs_begin_frame);
   void SubmitCompositorFrame(const LocalSurfaceId& local_surface_id,
                              CompositorFrame frame);
   void Require(const LocalSurfaceId& local_surface_id,
                const SurfaceSequence& sequence);
   void Satisfy(const SurfaceSequence& sequence);
   void AddChildFrameSink(const FrameSinkId& child_frame_sink_id);
   void RemoveChildFrameSink(const FrameSinkId& child_frame_sink_id);
 
@@ skipping 69 matching lines @@
   std::unordered_set<FrameSinkId, FrameSinkIdHash> child_frame_sinks_;
 
   base::WeakPtrFactory<CompositorFrameSinkSupport> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CompositorFrameSinkSupport);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_COMPOSITOR_FRAME_SINK_SUPPORT_H_