stagescale set

hi guys, i make one app for broadcasting my vtour , but i can not get the right stagescale.
i try <action name='mobilescale' autorun="preint' devices='mobile'> mul(stagescale,2); </action>
it works in app, bur the stagescale too big in the native broswer.
the useragent of the app is mozilla/5.0(linux;android 4.4.2; SM-N9006 Build/KOT49H)AppleWebkit/537.36(KHTML,like Gecko) Version/4.0 Chrome/30.0.0.0 Mobile Safari/537.36 DingdoneApp.65811.1.1.24(Dingdone Android 1.1.24)