Bug 1160333 - When denying permission, use the string 'PermissionDeniedError'. r=nsm

dom/push/Push.js

@@ -262,7 +262,7 @@ Push.prototype = {
         }.bind(this),
 
         function() {
-          reject("denied");
+          reject("PermissionDeniedError");
         }
       );
     }.bind(this));
@@ -286,7 +286,7 @@ Push.prototype = {
         }.bind(this),
 
         function() {
-          reject("denied");
+          reject("PermissionDeniedError");
         }
       );
     }.bind(this));