[iOS] Move keyboard accessory view code to separate target.

Bug: 738106
Change-Id: Ieba5f06da18e55a675ccac0082e0c0bef676abc4
Reviewed-on: https://chromium-review.googlesource.com/580991
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Jean-Fran├žois Geyelin <jif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#489332}
18 files changed