Enable options to remap CapsLock whenever an external keyboard is connected.

As per comments #16 and #17 on issue 167237, we will assume that most
external keyboards have a CapsLock key (chromeos external keyboards are
exceptions. However, there's no way to distinguish them at the moment).

This CL enables/disables the CapsLock remapping options in the keyboard
settings whenever there's an external keyboard is connected/disconnected
respectively.

BUG=167237

Review URL: https://codereview.chromium.org/1188693002

Cr-Commit-Position: refs/heads/master@{#334538}
2 files changed