Add Search item to Touchless NTP context menu.

Also adds support for showing the context menu on the All Apps button
with just the search entry.

Bug: 978458
Change-Id: I8c6a1229a84a7b60de2567c298ae1128096e9ae5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1677064
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Reviewed-by: Pavel Yatsuk <pavely@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672246}
5 files changed