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

src/gpu/gl/GrGLAssembleInterface.cpp

Index: src/gpu/gl/GrGLAssembleInterface.cpp
diff --git a/src/gpu/gl/GrGLAssembleInterface.cpp b/src/gpu/gl/GrGLAssembleInterface.cpp
index d7a0af802436791c5a69272e75ae62364992d062..82c4457c92d2ca592dd5e9ce45dd9f6c309b7ad7 100644
--- a/src/gpu/gl/GrGLAssembleInterface.cpp
+++ b/src/gpu/gl/GrGLAssembleInterface.cpp
@@ -755,6 +755,14 @@ const GrGLInterface* GrGLAssembleGLESInterface(void* ctx, GrGLGetProc get) {
         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;