vk: Use new style enum for KeyboardControllerState.

We switch KeyboardControllerState to the new style according to [1].

This also gives us a benefit that we no longer have to handle the
COUNT enum value with NOTREACHED.

[1] https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histograms/README.md#enum-histograms

TBR=sky@chromium.org

Bug: 845780
Change-Id: I84869a08e3f6187c767818643fd94db7dc590b08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1611070
Reviewed-by: Darren Shen <shend@chromium.org>
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660691}
4 files changed