vk: Move keyboard rebuild code from a11y controller to keyboard.

There's a corner case for the virtual keyboard where the keyboard has
to be rebuilt if we are going between compact and full layout (see bug).

Originally the code was in a11y controller, but it doesn't really make
sense to be there:

1. It's an implementation detail that should be encapsulated in the VK.
2. If SetAccessibilityKeyboardEnabled is called outside of a11y
   controller, then the logic breaks.

We move this to KeyboardController as part of the flag enable/clear
logic.

Bug: 946358
Change-Id: If2c4b9c632006406551304e29f8a96e13779315c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1551726
Commit-Queue: Darren Shen <shend@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#647937}
5 files changed