Add hooks for GL_EXT_debug_marker in gpu

src/gpu/gl/GrGLExtensions.cpp

Index: src/gpu/gl/GrGLExtensions.cpp
diff --git a/src/gpu/gl/GrGLExtensions.cpp b/src/gpu/gl/GrGLExtensions.cpp
index 33273e5f6511b41615919e43a5acee9c95344720..6d1b04d2cc6ced84e7f01420bf5f95f28302110e 100644
--- a/src/gpu/gl/GrGLExtensions.cpp
+++ b/src/gpu/gl/GrGLExtensions.cpp
@@ -120,6 +120,17 @@ bool GrGLExtensions::remove(const char ext[]) {
     }
 }
 
+void GrGLExtensions::add(const char ext[]) {
+    int idx = find_string(*fStrings, ext);
+    if (idx < 0) {
+        // This is not the most effecient approach since we end up doing a full sort of the
+        // extensions after the add
+        fStrings->push_back().set(ext);
+        SkTLessFunctionToFunctorAdaptor<SkString, extension_compare> cmp;
+        SkTQSort(&fStrings->front(), &fStrings->back(), cmp);
+    }
+}
+
 void GrGLExtensions::print(const char* sep) const {
     if (NULL == sep) {
         sep = " ";