Add CC to the GN build, work on GPU more

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")
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 gl_binding_output_dir = target_gen_dir
@@ skipping 283 matching lines @@
   ]
 
   args = [
     "--header-paths=" +
         rebase_path("//third_party/khronos", root_build_dir) + ":" +
         rebase_path("//third_party/mesa/src/include", root_build_dir),
     rebase_path(gl_binding_output_dir, root_build_dir),
   ]
 }
 
+config("gl_unittest_utils_config") {
+  include_dirs = [ gl_binding_output_dir ]
+}
+
+source_set("gl_unittest_utils") {
+  sources = [
+    "gl_mock.h",
+    "gl_mock.cc",
+    "$gl_binding_output_dir/gl_bindings_autogen_mock.cc",
+    "$gl_binding_output_dir/gl_bindings_autogen_mock.h",
+    "$gl_binding_output_dir/gl_mock_autogen_gl.h",
+  ]
+
+  configs += [ "//third_party/khronos:khronos_headers" ]
+  direct_dependent_configs = [ ":gl_unittest_utils_config" ]
+
+  deps = [
+    ":gl",
+    "//testing/gmock",
+  ]
+}
+
 if (is_android) {
   generate_jni("gl_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"
   }
 }