Consolidate message observer API for win and aura (and touch).

chrome/browser/chromeos/system_key_event_listener.h

Index: chrome/browser/chromeos/system_key_event_listener.h
diff --git a/chrome/browser/chromeos/system_key_event_listener.h b/chrome/browser/chromeos/system_key_event_listener.h
index 9cfd8447095e6052277a617eaf4ba0c889d41667..9b66995b20b1db17135e1925c61d7f695e4d1906 100644
--- a/chrome/browser/chromeos/system_key_event_listener.h
+++ b/chrome/browser/chromeos/system_key_event_listener.h
@@ -56,9 +56,10 @@ class SystemKeyEventListener : public WmMessageListener::Observer,
 
   AudioHandler* GetAudioHandler() const;
 
-#if defined(TOUCH_UI)
+#if defined(TOUCH_UI) || defined(USE_AURA)
   // MessageLoopForUI::Observer overrides.
-  virtual EventStatus WillProcessXEvent(XEvent* xevent) OVERRIDE;
+  virtual EventStatus WillProcessEvent(const NativeEvent& event) OVERRIDE;
+  virtual void DidProcessEvent(const NativeEvent& event) OVERRIDE;
 #else
   // This event filter intercepts events before they reach GDK, allowing us to
   // check for system level keyboard events regardless of which window has