Add search bar to Android password settings

By enabling the feature PasswordSearch, a search icon will appear in the
action bar in Chrome > Settings > Save Passwords.

Clicking the icon will trigger a search box that hides non-password
views.
Every newly typed letter will instantly filter passwords which
don't contain the query. Ignores case.

Update: instead of adding a new white icon, the ic_search is recolored.
Update: merged with WIP crrev/c/868213

Bug: 794108
Change-Id: I9b4e3c7754bb5b0cc56e3156a746bcbf44aa5bd3
Reviewed-on: https://chromium-review.googlesource.com/866830
Commit-Queue: Friedrich Horschig <fhorschig@chromium.org>
Reviewed-by: Maxim Kolosovskiy <kolos@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531891}