Makes tests either use mock compositor or mock WebGraphicsContext3D

ui/gfx/compositor/compositor_setup.h

+// 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_COMPOSITOR_COMPOSITOR_SETUP_H_
+#define UI_GFX_COMPOSITOR_COMPOSITOR_SETUP_H_
+#pragma once
+
+#include "ui/gfx/compositor/compositor_export.h"
+
+namespace ui {
+
+// Configures the compositor in such a way that it doesn't render anything.
+// Does nothing on platforms that aren't using the compositor.
+#if !defined(VIEWS_COMPOSITOR)
+// To centralize the ifdef to this file we define the function as doing nothing
+// on all platforms that don't use a compositor.
+COMPOSITOR_EXPORT void SetupTestCompositor() {}
+#else
+COMPOSITOR_EXPORT void SetupTestCompositor();
+
+// Disables the test compositor so that the normal compositor is used.
+COMPOSITOR_EXPORT void DisableTestCompositor();
+#endif
+
+}  // namespace ui
+
+#endif  // UI_GFX_COMPOSITOR_COMPOSITOR_SETUP_H_