Revert "Delete the ViewManager and WindowManager services."

services/view_manager/server_view_drawn_tracker_observer.h

+// Copyright 2015 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 SERVICES_VIEW_MANAGER_SERVER_VIEW_DRAWN_TRACKER_OBSERVER_H_
+#define SERVICES_VIEW_MANAGER_SERVER_VIEW_DRAWN_TRACKER_OBSERVER_H_
+
+namespace view_manager {
+
+class ServerView;
+
+class ServerViewDrawnTrackerObserver {
+ public:
+  // Invoked when the drawn state changes. If |is_drawn| is false |ancestor|
+  // identifies where the change occurred. In the case of a remove |ancestor| is
+  // the parent of the view that was removed. In the case of a visibility change
+  // |ancestor| is the parent of the view whose visibility changed.
+  virtual void OnDrawnStateChanged(ServerView* ancestor,
+                                   ServerView* view,
+                                   bool is_drawn) {}
+
+ protected:
+  virtual ~ServerViewDrawnTrackerObserver() {}
+};
+
+}  // namespace view_manager
+
+#endif  // SERVICES_VIEW_MANAGER_SERVER_VIEW_DRAWN_TRACKER_OBSERVER_H_