Remove the GrGLInterface callback mechanism.

src/gpu/gl/GrGLUtil.h

Index: src/gpu/gl/GrGLUtil.h
diff --git a/src/gpu/gl/GrGLUtil.h b/src/gpu/gl/GrGLUtil.h
index 8a3021cd5716fe684b4dd6bf5a49fa76c04c0e79..2f023f97bb95649069e32cddd3453e4f79eace1d 100644
--- a/src/gpu/gl/GrGLUtil.h
+++ b/src/gpu/gl/GrGLUtil.h
@@ -172,13 +172,6 @@ void GrGLClearErr(const GrGLInterface* gl);
     #define GR_GL_LOG_CALLS_IMPL(X)
 #endif
 
-// internal macro that does the per-GL-call callback (if necessary)
-#if GR_GL_PER_GL_FUNC_CALLBACK
-    #define GR_GL_CALLBACK_IMPL(IFACE) (IFACE)->fCallback(IFACE)
-#else
-    #define GR_GL_CALLBACK_IMPL(IFACE)
-#endif
-
 // makes a GL call on the interface and does any error checking and logging
 #define GR_GL_CALL(IFACE, X)                                    \
     do {                                                        \
@@ -190,7 +183,6 @@ void GrGLClearErr(const GrGLInterface* gl);
 // the caller wants to do its own glGetError() call and examine the error value.
 #define GR_GL_CALL_NOERRCHECK(IFACE, X)                         \
     do {                                                        \
-        GR_GL_CALLBACK_IMPL(IFACE);                             \
         (IFACE)->fFunctions.f##X;                               \
         GR_GL_LOG_CALLS_IMPL(X);                                \
     } while (false)
@@ -205,7 +197,6 @@ void GrGLClearErr(const GrGLInterface* gl);
 // same as GR_GL_CALL_RET but always skips the error check.
 #define GR_GL_CALL_RET_NOERRCHECK(IFACE, RET, X)                \
     do {                                                        \
-        GR_GL_CALLBACK_IMPL(IFACE);                             \
         (RET) = (IFACE)->fFunctions.f##X;                       \
         GR_GL_LOG_CALLS_IMPL(X);                                \
     } while (false)