ozone: Initialize a subsystem only if necessary.

ui/events/ozone/evdev/event_factory_evdev.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 UI_EVENTS_OZONE_EVDEV_EVENT_FACTORY_EVDEV_H_
 #define UI_EVENTS_OZONE_EVDEV_EVENT_FACTORY_EVDEV_H_
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
@@ skipping 34 matching lines @@
                          scoped_ptr<EventConverterEvdev> converter);
 
   // Close device at path (on UI thread).
   void DetachInputDevice(const base::FilePath& file_path);
 
   // DeviceEventObserver overrides:
   //
   // Callback for device add (on UI thread).
   virtual void OnDeviceEvent(const DeviceEvent& event) OVERRIDE;
 
+  // PlatformEventSource:
+  virtual void OnDispatcherListChanged() OVERRIDE;
+
   // Owned per-device event converters (by path).
   std::map<base::FilePath, EventConverterEvdev*> converters_;
 
   // Interface for scanning & monitoring input devices.
   DeviceManager* device_manager_;  // Not owned.
 
   // True if this was registered with |device_manager_|. This is needed since
   // StartProcessingEvents() is called multiple times (when a
   // WindowTreeHostOzone is created) but we shouldn't register this multiple
   // times.
@@ skipping 15 matching lines @@
 
   // Support weak pointers for attach & detach callbacks.
   base::WeakPtrFactory<EventFactoryEvdev> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(EventFactoryEvdev);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_OZONE_EVDEV_EVENT_FACTORY_EVDEV_H_