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 c41c5cf1ceaf69556a9e4ae276525831fa13f619..c52d60ef498a6c80b799b1edcac39c7b53a33006 100644
--- a/chrome/browser/chromeos/system_key_event_listener.h
+++ b/chrome/browser/chromeos/system_key_event_listener.h
@@ -51,9 +51,10 @@ class SystemKeyEventListener : public WmMessageListener::Observer,
   SystemKeyEventListener();
   virtual ~SystemKeyEventListener();
 
-#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 xevent) OVERRIDE;
+  virtual void WillProcessEvent(const NativeEvent xevent) 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