Adds special support to the device manager for keyboards devices.

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
index 8a763a6e9d666bf862901b4ba490d284dce59564..09ef7ec09b35c06400ff81bb397e79cfe6240317 100644
--- a/ui/events/device_hotplug_event_observer.h
+++ b/ui/events/device_hotplug_event_observer.h
@@ -6,6 +6,7 @@
 #define UI_EVENTS_DEVICE_HOTPLUG_EVENT_OBSERVER_H_
 
 #include "ui/events/events_base_export.h"
+#include "ui/events/keyboard_device.h"
 #include "ui/events/touchscreen_device.h"
 
 namespace ui {
@@ -15,9 +16,18 @@ class EVENTS_BASE_EXPORT DeviceHotplugEventObserver {
  public:
   virtual ~DeviceHotplugEventObserver() {}
 
-  // On a hotplug event this is called with the list of available devices.
+  // On a hotplug event this is called with the list of available touchscreen
+  // devices.
   virtual void OnTouchscreenDevicesUpdated(
       const std::vector<TouchscreenDevice>& devices) = 0;
+
+  // On a hotplug event this is called with the list of available keyboard
+  // devices.
+  virtual void OnKeyboardDevicesUpdated(
+      const std::vector<KeyboardDevice>& devices) = 0;
+
+  // Called on any hotplug event.
+  virtual void OnInputDeviceConfigurationChanged();
 };
 
 }  // namespace ui