vk: Use synchronous API for keyboard controller.

With the MASH cleanup, we are converting mojo async APIs back into C++
sync APIs. This simplifies the code a lot.

Bug: 958203
Change-Id: Ia389ca4c0fc554a8b0082a378010ad7fd758c4aa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1646685
Commit-Queue: Darren Shen <shend@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#668663}
12 files changed