Address the TODOs in the PushMessagingBrowserTest for the endpoint merge.

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
Committed: https://crrev.com/7015c4d2419cd07f4643dd33321991ee81dcb6a2
Cr-Commit-Position: refs/heads/master@{#328523}

[Peter Beverloo, 2015-04-20 18:10:39]

peter@chromium.org changed reviewers:
+ mvanouwerkerk@chromium.org

[Peter Beverloo, 2015-04-20 18:10:39]

+mvanouwerkerk

[Michael van Ouwerkerk, 2015-04-21 11:03:13]

lgtm

[Peter Beverloo, 2015-05-06 12:43:40]

The CQ bit was checked by peter@chromium.org

[Peter Beverloo, 2015-05-06 12:43:41]

The patchset sent to the CQ was uploaded after l-g-t-m from
mvanouwerkerk@chromium.org
Link to the patchset: https://codereview.chromium.org/1078873004/#ps20001
(title: "rebase")

[commit-bot: I haz the power, 2015-05-06 12:43:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1078873004/20001

[commit-bot: I haz the power, 2015-05-06 13:41:37]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-06 13:42:43]

Patchset 2 (id:??) landed as
https://crrev.com/7015c4d2419cd07f4643dd33321991ee81dcb6a2
Cr-Commit-Position: refs/heads/master@{#328523}