Fix build bustage.

widget/src/gtk/nsSound.h

@@ -33,10 +33,6 @@ class nsSound : public nsISound {
   nsSound();
   virtual ~nsSound();
 
-  NS_IMETHOD Play(nsIURI *aURI);
-  NS_IMETHOD Init(void);
-  NS_IMETHOD Beep(void);
-
   NS_DECL_ISUPPORTS
   NS_DECL_NSISOUND