fixup! Add high touch sensitivity and hovering to InputService

I brought back the SettingsObserver code as that felt simpler
and enough for our purposes here for just this one setting,
as opposed to going down the rabbit hole of re-implementing
SecureSettingsChangeCallback and SecureSettingsWrapper for us.

Change-Id: Ib278fb84d84b057f2a7f0bd3acb3d21baf5d1db4