fixed scale bug on android browser

## before
![screenshot_2014-09-12-16-54-31](https://cloud.githubusercontent.com/assets/1064585/4247054/a8aa7ff4-3a54-11e4-8607-bec16b88865b.png)


## after
![screenshot_2014-09-12-16-59-07](https://cloud.githubusercontent.com/assets/1064585/4247057/bc9f41e8-3a54-11e4-8f3e-04d86284d74d.png)