GitLab

Allows user to input fake PhoneHub notification data, and for
notifications to eventually display via FakeNotificationManager. User
can send, update, delete, and view a list of notifications.

This CL also cleans up some of the other phonehub forms in
chrome://multidevice-internals.

Screenshots:
https://screenshot.googleplex.com/9XNVYwEeAQUZeWG Disabled Send button
https://screenshot.googleplex.com/4nz5PaMH8bfLbdR Enabled Send button
https://screenshot.googleplex.com/AUsqtxMgJwMwHBs Sent notification
https://screenshot.googleplex.com/5nCmMZW6xcviatK Updated! UI
https://screenshot.googleplex.com/3fnNdKZcFDCWgcL Multiple notifications
https://screenshot.googleplex.com/86y2Mqa2C8AmZSP Unique id & inline id

Bug: 1106937
Change-Id: Ie5aecd70a03b6e84aa8745a2ece421e0d8086970
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2411546
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807272}