Implement SkGLContext swapBuffers with fence syncs

src/gpu/gl/GrGLAssembleInterface.h

 
 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gl/GrGLInterface.h"
 
-typedef void(*GrGLFuncPtr)();
 typedef GrGLFuncPtr (*GrGLGetProc)(void* ctx, const char name[]);
 
 
 /**
  * Generic function for creating a GrGLInterface for an either OpenGL or GLES. It calls
  * get() to get each function address. ctx is a generic ptr passed to and interpreted by get().
  */
 const GrGLInterface* GrGLAssembleInterface(void* ctx, GrGLGetProc get);
 
 /**
  * Generic function for creating a GrGLInterface for an OpenGL (but not GLES) context. It calls
  * get() to get each function address. ctx is a generic ptr passed to and interpreted by get().
  */
 const GrGLInterface* GrGLAssembleGLInterface(void* ctx, GrGLGetProc get);
 
 /**
  * Generic function for creating a GrGLInterface for an OpenGL ES (but not Open GL) context. It
  * calls get() to get each function address. ctx is a generic ptr passed to and interpreted by
  * get().
  */
 const GrGLInterface* GrGLAssembleGLESInterface(void* ctx, GrGLGetProc get);