Move Settings button to DialogPlate from CaptionBar.

This involved adding a settings button to both the keyboard and voice
input modality child layouts of DialogPlate. I used two distinct views,
rather than a single view, to represent settings button to keep the
layout logic as simple as possible.

See bug for demo.

Bug: b:110263671
Change-Id: I6caf1cb3c79cd789b0598cdc3771090b187cb634
Reviewed-on: https://chromium-review.googlesource.com/1103153
Commit-Queue: David Black <dmblack@google.com>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568680}
7 files changed