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This adds support for validating the device name that a user enters.
Validation happens as the user types and also when they try to save the
name. If an invalid name is detected, an error message will appear and
the "Done" button will be disabled.

Screenshots:
  https://screenshot.googleplex.com/3gnC6aQVyj4YmkX.png
  https://screenshot.googleplex.com/5arMAbok2MgfioU.png
  https://screenshot.googleplex.com/BEbCJ9LteRAYFpv.png

Bug: b:161297140
Change-Id: I3290eb92222cd796a1dede3ce603da5cc44940bf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2424675
Commit-Queue: Michael Hansen <hansenmichael@google.com>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Alex Gough <ajgo@chromium.org>
Reviewed-by: James Vecore <vecore@google.com>
Cr-Commit-Position: refs/heads/master@{#811482}