Add swapBuffer call to SkGLContextHelper.

include/gpu/gl/SkDebugGLContext.h

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkDebugGLContext_DEFINED
 #define SkDebugGLContext_DEFINED
 
 #include "SkGLContextHelper.h"
 
 class SkDebugGLContext : public SkGLContextHelper {
 
 public:
     SkDebugGLContext() {};
 
     virtual void makeCurrent() const SK_OVERRIDE {};
+    virtual void swapBuffers() const SK_OVERRIDE {};
 
 protected:
     virtual const GrGLInterface* createGLContext() SK_OVERRIDE;
 
     virtual void destroyGLContext() SK_OVERRIDE {};
 };
 
 #endif