Fixed #3568:  Correct a bug that it can't see the progress text when contentScaleFactor sets.
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-html5 into Iss3568_FixLabelAtlasBug
Merge pull request #1433 from dingpinglv/Iss3568_FixLabelAtlasBug

Fixed #3568: Correct a bug that it can't see the progress text when contentScaleFactor sets.