Add SurfaceDisplayOutputSurface unittests

cc/surfaces/onscreen_display_client.h

 // Copyright 2014 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_ONSCREEN_DISPLAY_CLIENT_H_
 #define CC_SURFACES_ONSCREEN_DISPLAY_CLIENT_H_
 
 #include "cc/surfaces/display_client.h"
 
 #include "base/compiler_specific.h"
@@ skipping 31 matching lines @@
   }
 
   // DisplayClient implementation.
   void CommitVSyncParameters(base::TimeTicks timebase,
                              base::TimeDelta interval) override;
   void OutputSurfaceLost() override;
   void SetMemoryPolicy(const ManagedMemoryPolicy& policy) override;
 
   bool output_surface_lost() { return output_surface_lost_; }
 
- private:
+ protected:
   scoped_ptr<OutputSurface> output_surface_;
   scoped_ptr<Display> display_;
   scoped_ptr<SyntheticBeginFrameSource> synthetic_begin_frame_source_;
   scoped_ptr<DisplayScheduler> scheduler_;
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
   SurfaceDisplayOutputSurface* surface_display_output_surface_;
   bool output_surface_lost_;
 
   DISALLOW_COPY_AND_ASSIGN(OnscreenDisplayClient);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_ONSCREEN_DISPLAY_CLIENT_H_