Move touchscreen device caching to DeviceDataManager

ui/events/device_hotplug_event_observer.h

Index: ui/events/device_hotplug_event_observer.h
diff --git a/ui/events/device_hotplug_event_observer.h b/ui/events/device_hotplug_event_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..8a763a6e9d666bf862901b4ba490d284dce59564
--- /dev/null
+++ b/ui/events/device_hotplug_event_observer.h
@@ -0,0 +1,25 @@
+// 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_DEVICE_HOTPLUG_EVENT_OBSERVER_H_
+#define UI_EVENTS_DEVICE_HOTPLUG_EVENT_OBSERVER_H_
+
+#include "ui/events/events_base_export.h"
+#include "ui/events/touchscreen_device.h"
+
+namespace ui {
+
+// Listener for specific input device hotplug events.
+class EVENTS_BASE_EXPORT DeviceHotplugEventObserver {
+ public:
+  virtual ~DeviceHotplugEventObserver() {}
+
+  // On a hotplug event this is called with the list of available devices.
+  virtual void OnTouchscreenDevicesUpdated(
+      const std::vector<TouchscreenDevice>& devices) = 0;
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_DEVICE_HOTPLUG_EVENT_OBSERVER_H_