[Android] Display favicons in password accessory sheet

This CL adds an image view to all usernames in the passwords accessory
sheet which separates username/password groups visually.
It also indicates the origin of the credentials.

The icons are loaded by origin on the native side. If icons are
requested multiple times, they will be grouped by origin and result
in only one request to the FaviconService.
Already requested icons are cached - when one of these is requested,
the callback will return synchronously instead of async.

Bug: 853748
Change-Id: Ia97c5c62710daf709d7ee19d732d2e226ac7634f
Reviewed-on: https://chromium-review.googlesource.com/1138319
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Friedrich Horschig <fhorschig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577876}
16 files changed