Converts overview to use common ash types

ash/wm/overview/scoped_overview_animation_settings_factory.cc

+// Copyright 2016 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.
+
+#include "ash/wm/overview/scoped_overview_animation_settings_factory.h"
+
+#include "base/logging.h"
+
+namespace ash {
+
+// static
+ScopedOverviewAnimationSettingsFactory*
+    ScopedOverviewAnimationSettingsFactory::instance_ = nullptr;
+
+// static
+ScopedOverviewAnimationSettingsFactory*
+ScopedOverviewAnimationSettingsFactory::Get() {
+  return instance_;
+}
+
+ScopedOverviewAnimationSettingsFactory::
+    ScopedOverviewAnimationSettingsFactory() {
+  DCHECK(!instance_);
+  instance_ = this;
+}
+
+ScopedOverviewAnimationSettingsFactory::
+    ~ScopedOverviewAnimationSettingsFactory() {
+  DCHECK_EQ(instance_, this);
+  instance_ = nullptr;
+}
+
+}  // namespace ash