从 qq小游戏子域不能用lable 继续讨论：
Canvas.js:60 Uncaught TypeError: Cannot redefine property: clientWidth
at Function.defineProperty ()
at new Canvas (Canvas.js:60)
at HTMLDocument.createElement (document.js:55)
at Object.getColorizedImage (cocos2d-js-min.a8f43.js:1)
at Object.draw (cocos2d-js-min.a8f43.js:1)
at r._commitComp (cocos2d-js-min.a8f43.js:1)
at g.150.y._render (cocos2d-js-min.a8f43.js:1)
at g.150.y._color (cocos2d-js-min.a8f43.js:1)
at g.150.y._worldTransform (cocos2d-js-min.a8f43.js:1)
at g.150.y._children (cocos2d-js-min.a8f43.js:1)