Fix PingLoaderTest crashing the next test

Fix PingLoaderTest crashing the next test

Pings can't be cancelled or otherwise accessed once started, so ensure the
mocked network request is served before the test completes and the mocked
load is unregistered.

BUG=682567
Review-Url: https://codereview.chromium.org/2682533002
Cr-Commit-Position: refs/heads/master@{#448693}
Committed: https://chromium.googlesource.com/chromium/src/+/2d15a4c1a0667a7e9f6d46946a39ba4a79be518f

[Nate Chapin, 2017-02-06 23:52:35]

The CQ bit was checked by japhet@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-02-06 23:53:38]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Nate Chapin, 2017-02-06 23:54:38]

japhet@chromium.org changed reviewers:
+ toyoshim@chromium.org

[Nate Chapin, 2017-02-06 23:54:38]

toyoshim@: Would you like to review, since you filed the bug? :)

[commit-bot: I haz the power, 2017-02-07 01:18:20]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-07 01:18:21]

Dry run: This issue passed the CQ dry run.

[Takashi Toyoshima, 2017-02-07 07:18:05]

thanks. lgtm.

[Nate Chapin, 2017-02-07 19:18:19]

The CQ bit was checked by japhet@chromium.org

[commit-bot: I haz the power, 2017-02-07 19:19:13]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-02-07 19:28:27]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1486495099067400, "parent_rev":
"84352d5d869c9c5a8092f4dc44dab7a6950a3b18", "commit_rev":
"2d15a4c1a0667a7e9f6d46946a39ba4a79be518f"}

[commit-bot: I haz the power, 2017-02-07 19:29:02]

Description was changed from

==========
Fix PingLoaderTest crashing the next test

Pings can't be cancelled or otherwise accessed once started, so ensure the
mocked network request is served before the test completes and the mocked
load is unregistered.

BUG=682567
==========

to

==========
Fix PingLoaderTest crashing the next test

Pings can't be cancelled or otherwise accessed once started, so ensure the
mocked network request is served before the test completes and the mocked
load is unregistered.

BUG=682567

Review-Url: https://codereview.chromium.org/2682533002
Cr-Commit-Position: refs/heads/master@{#448693}
Committed:
https://chromium.googlesource.com/chromium/src/+/2d15a4c1a0667a7e9f6d46946a39...
==========

[commit-bot: I haz the power, 2017-02-07 19:29:03]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/2d15a4c1a0667a7e9f6d46946a39...