Push API: Don't unsubscribe when finding Service Worker fails

Push API: Don't unsubscribe when finding Service Worker fails

Failing to find a service worker might be temporary, so we shouldn't
unsubscribe in this case. Continue to unsubscribe if the Service Worker
is actually not found (e.g. because it has been unregistered).

Also adds more UMA in this area.

BUG=642139
Review-Url: https://codereview.chromium.org/2361113002
Cr-Commit-Position: refs/heads/master@{#420447}
(cherry picked from commit 983872d32d2b818957e3ba7714b7a822a27e0dd8)

Committed: https://chromium.googlesource.com/chromium/src/+/d9b986d87105a963f619d0dd6f6931270721b13b

[johnme, 2016-09-26 15:20:48]

Description was changed from

==========
Push API: Don't unsubscribe when finding Service Worker fails

Failing to find a service worker might be temporary, so we shouldn't
unsubscribe in this case. Continue to unsubscribe if the Service Worker
is actually not found (e.g. because it has been unregistered).

Also adds more UMA in this area.

BUG=642139

Review-Url: https://codereview.chromium.org/2361113002
Cr-Commit-Position: refs/heads/master@{#420447}
(cherry picked from commit 983872d32d2b818957e3ba7714b7a822a27e0dd8)
==========

to

==========
Push API: Don't unsubscribe when finding Service Worker fails

Failing to find a service worker might be temporary, so we shouldn't
unsubscribe in this case. Continue to unsubscribe if the Service Worker
is actually not found (e.g. because it has been unregistered).

Also adds more UMA in this area.

BUG=642139

Review-Url: https://codereview.chromium.org/2361113002
Cr-Commit-Position: refs/heads/master@{#420447}
(cherry picked from commit 983872d32d2b818957e3ba7714b7a822a27e0dd8)

Committed:
https://chromium.googlesource.com/chromium/src/+/d9b986d87105a963f619d0dd6f69...
==========

[johnme, 2016-09-26 15:20:49]

Committed patchset #1 (id:1) manually as
d9b986d87105a963f619d0dd6f6931270721b13b.