Controllers must have buttons and a movement mechanism.

Some devices have joystick axes or DPad keys, but no gamepad buttons (or vice
versa). We shouldn't count these as gamepads since games can't really be
expected to work with this setup in the general case. Instead, require that a
device has a movement mechanism (joystick axes or DPad buttons), as well as at
least one gamepad button before considering it a controller.

Bug: 13432364
Change-Id: I64372e69d29c775094e2b1faa89714da8c29e2be