Normally, F2 causes the browser to go full-screen, showing only the
Apple screen. However, in Chrome, the user can exit full-screen mode
by pressing ESC. Since ESC is used frequently on the Apple //e, this
limits the utility of full-screen mode.
To work around this problem, this change adds Shift-F2, which will
make the Apple fill the window without going full-screen. This allows
the user to go make the window full-screen in some other way, thus
enabling the use of the ESC key.
Note that the method used is almost entirely implemented in CSS, with
just a few lines of code to change the classes on some elements. This
may not be the best long-term way of implementing this feature.