Added switch to disable specified GL extensions.

ui/gl/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
@@ skipping 262 matching lines @@
   configs += [ "//third_party/khronos:khronos_headers" ]
 
   deps = [
     ":gl",
     "//testing/gmock",
   ]
 }
 
 test("gl_unittests") {
   sources = [
+    "gl_api_unittest.cc",
     "test/run_all_unittests.cc",
   ]
 
   deps = [
     ":gl",
     "//base",
     "//base/test:test_support",
     "//testing/gtest",
   ]
 }
 
 if (is_android) {
   generate_jar_jni("surface_jni_headers") {
     jni_package = "ui/gl"
     classes = [ "android/view/Surface.class" ]
   }
 
   generate_jni("gl_jni_headers") {
     deps = [
       ":surface_jni_headers",
     ]
     sources = [
       "../android/java/src/org/chromium/ui/gl/SurfaceTextureListener.java",
       "../android/java/src/org/chromium/ui/gl/SurfaceTexturePlatformWrapper.java",
     ]
     jni_package = "ui/gl"
   }
 }