Add work around for devices/API filters that claim GL_KHR_debug support but don't provide functions

src/gpu/gl/GrGLAssembleInterface.cpp

 
 /*
  * 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 "GrGLAssembleInterface.h"
@@ skipping 737 matching lines @@
     }
 
     if (extensions.has("GL_KHR_debug")) {
         GET_PROC_SUFFIX(DebugMessageControl, KHR);
         GET_PROC_SUFFIX(DebugMessageInsert, KHR);
         GET_PROC_SUFFIX(DebugMessageCallback, KHR);
         GET_PROC_SUFFIX(GetDebugMessageLog, KHR);
         GET_PROC_SUFFIX(PushDebugGroup, KHR);
         GET_PROC_SUFFIX(PopDebugGroup, KHR);
         GET_PROC_SUFFIX(ObjectLabel, KHR);
+        // In general we have a policy against removing extension strings when the driver does
+        // not provide function pointers for an advertised extension. However, because there is a
+        // known device that advertises GL_KHR_debug but fails to provide the functions and this is
+        // a debugging- only extension we've made an exception. This also can happen when using
+        // APITRACE.
+        if (!interface->fFunctions.fDebugMessageControl) {
+            extensions.remove("GL_KHR_debug");
+        }
     }
 
     interface->fStandard = kGLES_GrGLStandard;
     interface->fExtensions.swap(&extensions);
 
     return interface;
 }