mus: Add EventObserver to allow passively listening to UI events

components/mus/ws/window_server.h

 // 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.
 
 #ifndef COMPONENTS_MUS_WS_WINDOW_SERVER_H_
 #define COMPONENTS_MUS_WS_WINDOW_SERVER_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 168 matching lines @@
   void ProcessWindowHierarchyChanged(const ServerWindow* window,
                                      const ServerWindow* new_parent,
                                      const ServerWindow* old_parent);
   void ProcessWindowReorder(const ServerWindow* window,
                             const ServerWindow* relative_window,
                             const mojom::OrderDirection direction);
   void ProcessWindowDeleted(const ServerWindow* window);
   void ProcessWillChangeWindowPredefinedCursor(ServerWindow* window,
                                                int32_t cursor_id);
 
+  // Sends an |event| to all WindowTrees belonging to |user_id| that might be
+  // observing events. Skips |ignore_tree| if it is non-null.
+  void SendToEventObservers(const ui::Event& event,
+                            const UserId& user_id,
+                            WindowTree* ignore_tree);
+
  private:
   friend class Operation;
 
   using WindowTreeMap = std::map<ConnectionSpecificId, scoped_ptr<WindowTree>>;
 
   struct InFlightWindowManagerChange {
     // Identifies the client that initiated the change.
     ConnectionSpecificId connection_id;
 
     // Change id supplied by the client.
@@ skipping 101 matching lines @@
 
   WindowManagerFactoryRegistry window_manager_factory_registry_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowServer);
 };
 
 }  // namespace ws
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_WS_WINDOW_SERVER_H_