Add hooks for GL_EXT_debug_marker in gpu

src/gpu/gl/iOS/GrGLCreateNativeInterface_iOS.cpp

Index: src/gpu/gl/iOS/GrGLCreateNativeInterface_iOS.cpp
diff --git a/src/gpu/gl/iOS/GrGLCreateNativeInterface_iOS.cpp b/src/gpu/gl/iOS/GrGLCreateNativeInterface_iOS.cpp
index d8b4e1f8ccf77071f2c1686f6a4e792da550bd9e..1c34452f9a0471a63cf86d7d146f8edd1d0fc9fa 100644
--- a/src/gpu/gl/iOS/GrGLCreateNativeInterface_iOS.cpp
+++ b/src/gpu/gl/iOS/GrGLCreateNativeInterface_iOS.cpp
@@ -144,6 +144,11 @@ const GrGLInterface* GrGLCreateNativeInterface() {
     functions->fGenVertexArrays = glGenVertexArraysOES;
 #endif
 
+    if (extensions.has("GL_EXT_debug_marker")) {
+      functions->fInsertEventMarker = glInsertEventMarkerEXT;

[bsalomon, 2014/02/20 22:14:13]

I think we either have to dynamically load the function addrs or guard this with
#if GL_EXT_... or else these symbols won't be found.

+      functions->fPushGroupMarker = glPushGroupMarkerEXT;
+      functions->fPopGroupMarker = glPopGropuMarkerEXT;
+    }
     interface->fStandard = kGLES_GrGLStandard;
     interface->fExtensions.init(kGLES_GrGLStandard, glGetString, NULL, glGetIntegerv);