Fix MSVC warnings about assigning a wider variable into a narrower one resulting from the checkin for bug 338678. r=brendan

js/src/jsapi.c

@@ -3695,7 +3695,7 @@ JS_DefineFunctions(JSContext *cx, JSObject *obj, JSFunctionSpec *fs)
                                     fs->nargs + 1, flags);
             if (!fun)
                 return JS_FALSE;
-            fun->u.n.extra = fs->extra;
+            fun->u.n.extra = (uint16)fs->extra;
 
             /*
              * As jsapi.h notes, fs must point to storage that lives as long
@@ -3708,7 +3708,7 @@ JS_DefineFunctions(JSContext *cx, JSObject *obj, JSFunctionSpec *fs)
         fun = JS_DefineFunction(cx, obj, fs->name, fs->call, fs->nargs, flags);
         if (!fun)
             return JS_FALSE;
-        fun->u.n.extra = fs->extra;
+        fun->u.n.extra = (uint16)fs->extra;
     }
     return JS_TRUE;
 }