Remove _JOYSTICK and _MOBILE locations from keyboard events.

These definitions have been removed from the DOM3 spec.

This is a trivial change that involves removing TODO comments and "not implemented" tests.

BUG=265446

Review URL: https://chromiumcodereview.appspot.com/23636017

git-svn-id: svn://svn.chromium.org/blink/trunk@157809 bbb929c8-8fbe-4397-9dbb-9b2b20218538