GUI behavior when changing displays

[jhakala]

Currently the GUI's driver/spectator recognition scheme involves using a browser "fingerprinting" method that parses several pieces of information supplied by the user's browser to identify whether a user visiting the GUI is driving or spectating. One of the pieces of information used is the user's screen size/resolution. Therefore if a user unplugs an external monitor while driving, it can have the effect of putting the driver into spectator mode.

This is fine (I don't think the fingerprinting method should be changed; if you change monitors during driving it's not a big deal to click one button to go back into driver mode), but currently when this happens, the driver enters spectator mode, and instead of the "Spectate" button going away and the "Take Control" button popping up (the desired behavior), the "Spectate" button remains in the GUI and no "Take Control" button appears. This should be fixed.