Add hooks for GL_EXT_debug_marker in gpu

BUG=skia:
R=bsalomon@google.com

Author: egdaniel@google.com

Review URL: https://codereview.chromium.org/174123003

git-svn-id: http://skia.googlecode.com/svn/trunk@13538 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/gl/mesa/GrGLCreateMesaInterface.cpp b/src/gpu/gl/mesa/GrGLCreateMesaInterface.cpp
index 5931444..0ce6d2f 100644
--- a/src/gpu/gl/mesa/GrGLCreateMesaInterface.cpp
+++ b/src/gpu/gl/mesa/GrGLCreateMesaInterface.cpp
@@ -221,6 +221,12 @@
         }
         GR_GL_GET_PROC(BindFragDataLocationIndexed);
 
+        if (extensions.has("GL_EXT_debug_marker")) {
+            GR_GL_GET_PROC_SUFFIX(InsertEventMarker, EXT);
+            GR_GL_GET_PROC_SUFFIX(PopGroupMarker, EXT);
+            GR_GL_GET_PROC_SUFFIX(PushGroupMarker, EXT);
+        }
+
         interface->fStandard = kGL_GrGLStandard;
         interface->fExtensions.swap(&extensions);