Add a provider for the Passwords UI in Settings

This CL introduces ManagePasswordsUIProvider, a class which aims to allow
for alternative UI surfaces to be shown if available.

Bug: 903249
Change-Id: I8c03f2f539772044bd5ba0fa944fd5e441d43c76
Reviewed-on: https://chromium-review.googlesource.com/c/1326488
Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Ioana Pandele <ioanap@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606837}
4 files changed