Fix up compositor mocking.

ui/gfx/test/gfx_test_utils.h

Index: ui/gfx/test/gfx_test_utils.h
diff --git a/ui/gfx/test/gfx_test_utils.h b/ui/gfx/test/gfx_test_utils.h
new file mode 100644
index 0000000000000000000000000000000000000000..da2b2bec3780d2addea5c66e058f8a6f86cbd1cd
--- /dev/null
+++ b/ui/gfx/test/gfx_test_utils.h
@@ -0,0 +1,19 @@
+// Copyright (c) 2011 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.
+
+#ifndef UI_GFX_GFX_TEST_UTILS_H_
+#define UI_GFX_GFX_TEST_UTILS_H_
+#pragma once
+
+namespace ui {
+namespace gfx_test_utils {
+
+// Called by tests that want to use a mocked compositor.
+// Implementation is no-oped on platforms that don't use a compositor.
+void SetupTestCompositor();
+
+}  // namespace gfx_test_utils
+}  // namespace ui
+
+#endif  // UI_GFX_GFX_TEST_UTILS_H_