Fix variations crashes when the chosen trial group is not in study.

Fix variations crashes when the chosen trial group is not in study.

Adds a couple tests that would hit that code path.

BUG=724957
Review-Url: https://codereview.chromium.org/2919143002
Cr-Commit-Position: refs/heads/master@{#476856}
Committed: https://chromium.googlesource.com/chromium/src/+/3cac35f9fdcde39a17ac119d9190139b90f0b75a

[Alexei Svitkine (slow), 2017-06-02 20:36:59]

asvitkine@chromium.org changed reviewers:
+ jwd@chromium.org

[jwd, 2017-06-02 20:56:43]

lgtm

[Alexei Svitkine (slow), 2017-06-02 21:03:18]

The CQ bit was checked by asvitkine@chromium.org

[commit-bot: I haz the power, 2017-06-02 21:03:52]

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, 2017-06-03 00:20:20]

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

[commit-bot: I haz the power, 2017-06-03 00:20:21]

Try jobs failed on following builders:
  linux_android_rel_ng on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_androi...)

[Alexei Svitkine (slow), 2017-06-03 00:28:05]

The CQ bit was checked by asvitkine@chromium.org

[commit-bot: I haz the power, 2017-06-03 00:28:42]

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, 2017-06-03 02:02:29]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1496449685292520, "parent_rev":
"76848ad61df944e68cda21e4fbc5e2565bd80f08", "commit_rev":
"3cac35f9fdcde39a17ac119d9190139b90f0b75a"}

[commit-bot: I haz the power, 2017-06-03 02:02:40]

Description was changed from

==========
Fix variations crashes when the chosen trial group is not in study.

Adds a couple tests that would hit that code path.

BUG=724957
==========

to

==========
Fix variations crashes when the chosen trial group is not in study.

Adds a couple tests that would hit that code path.

BUG=724957

Review-Url: https://codereview.chromium.org/2919143002
Cr-Commit-Position: refs/heads/master@{#476856}
Committed:
https://chromium.googlesource.com/chromium/src/+/3cac35f9fdcde39a17ac119d9190...
==========

[commit-bot: I haz the power, 2017-06-03 02:02:41]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/3cac35f9fdcde39a17ac119d9190...