Remove the GrGLInterface callback mechanism.

include/gpu/gl/GrGLInterface.h

Index: include/gpu/gl/GrGLInterface.h
diff --git a/include/gpu/gl/GrGLInterface.h b/include/gpu/gl/GrGLInterface.h
index 1e2ac8f85b12ed06ffc178d97411593dd58fc53b..cbf9b1a59fc9917c003aa89bd137d9463cf4b0a4 100644
--- a/include/gpu/gl/GrGLInterface.h
+++ b/include/gpu/gl/GrGLInterface.h
@@ -76,11 +76,6 @@ const SK_API GrGLInterface* GrGLCreateNullInterface();
  */
 const GrGLInterface* GrGLCreateDebugInterface();
 
-#if GR_GL_PER_GL_FUNC_CALLBACK
-typedef void (*GrGLInterfaceCallbackProc)(const GrGLInterface*);
-typedef intptr_t GrGLInterfaceCallbackData;
-#endif
-
 /** Function that returns a new interface identical to "interface" but without support for
     GL_NV_path_rendering. */
 const GrGLInterface* GrGLInterfaceRemoveNVPR(const GrGLInterface*);
@@ -492,12 +487,6 @@ public:
         GrGLFunction<GrEGLDestroyImageProc> fEGLDestroyImage;
     } fFunctions;
 
-    // Per-GL func callback
-#if GR_GL_PER_GL_FUNC_CALLBACK
-    GrGLInterfaceCallbackProc fCallback;
-    GrGLInterfaceCallbackData fCallbackData;
-#endif
-
     // This exists for internal testing.
     virtual void abandon() const {}
 };