Address the TODOs in the PushMessagingBrowserTest for the endpoint merge.

The endpoint value checks have been put back in place, now following
the new format and only checking the |endpoint| value. Inclusion of the
subscription Id in the endpoint is covered by Blink's layout tests.

This CL is part of a three-sided patch:
  [1] https://codereview.chromium.org/1099673002/
  [2] https://codereview.chromium.org/1084683003/
  [3] This CL.

BUG=477401

Review URL: https://codereview.chromium.org/1078873004

Cr-Commit-Position: refs/heads/master@{#328523}
2 files changed