Bug 672092, follow up fix in nsXULMenuAccessible::KeyboardShortcut, r=tbsaunde

accessible/src/xul/nsXULMenuAccessible.cpp

@@ -465,7 +465,7 @@ nsXULMenuitemAccessible::KeyboardShortcut() const
 
   PRUint32 modifierMask = 0;
   if (modifiersStr.Find("shift") != -1)
-    modifierMask != KeyBinding::kShift;
+    modifierMask |= KeyBinding::kShift;
   if (modifiersStr.Find("alt") != -1)
     modifierMask |= KeyBinding::kAlt;
   if (modifiersStr.Find("meta") != -1)