So the browser object is already in your project, as I expected..
Like I said in your other thread, the browser object has an action " lock orientation"
You can use this action to lock the orientation..
From the browser manual
Lock orientation
Unlock orientation
Lock the display of the game to a portrait or landscape mode only, if the current platform supports this. This only has effect on mobile devices. The game may have to already be displaying in fullscreen (using the Request fullscreen action) before the orientation can be locked. Unlocking the orientation restores whatever behavior was set before locking, such as automatically changing orientation depending on the way the device is being held.