Bug 828197 - make the onpair screen of bluescreen properly handle home key

[Root Cause]
The on pair screen will disappear once the keyboard is shown up because we listen to 'resize' event and close the window.
What we want is to close the window when [Home] button is pressed but not for keyboard change.

[Solution]
The only (hacky) way we can know the home screen is pressed is still from window "resize" event, and here we check window.innerHeight to be < 200, because it is 40px when the attentation screen is in active status bar mode.