Fix app menu button preferred size issue.

App menu now sets its label text context to toolbar button, like other
toolbar buttons.

Also prevent toolbar and app menu buttons from unnecessarily destroying
and recreating empty borders if the inset size has not changed.

Bug: 931575
Change-Id: Id2b7e146a97b1da56f08caa9b79b4c7072c9de04
Reviewed-on: https://chromium-review.googlesource.com/c/1474687
Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632703}
5 files changed