Add test to check for crash caused by stale WebContents in chrome://interstitials

Add test to check for crash caused by stale WebContents in chrome://interstitials

BUG=611706
Review-Url: https://codereview.chromium.org/2618573002
Cr-Commit-Position: refs/heads/master@{#441798}
Committed: https://chromium.googlesource.com/chromium/src/+/7b1ab28d89a2ff18515b3c699dfc02a15aae84ee

[meacer, 2017-01-04 23:55:50]

meacer@chromium.org changed reviewers:
+ estark@chromium.org

[meacer, 2017-01-04 23:55:50]

PTAL?

[estark, 2017-01-05 16:23:06]

lgtm

[meacer, 2017-01-05 18:27:04]

The CQ bit was checked by meacer@chromium.org

[commit-bot: I haz the power, 2017-01-05 18:27:33]

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, 2017-01-05 19:26:45]

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

[commit-bot: I haz the power, 2017-01-05 19:26:45]

Try jobs failed on following builders:
  linux_chromium_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[meacer, 2017-01-05 21:47:31]

Looks like the test caught a new bug.

[meacer, 2017-01-05 21:47:35]

The CQ bit was checked by meacer@chromium.org

[meacer, 2017-01-05 21:47:36]

The patchset sent to the CQ was uploaded after l-g-t-m from estark@chromium.org
Link to the patchset: https://codereview.chromium.org/2618573002/#ps20001
(title: "Fix browser side navigation")

[commit-bot: I haz the power, 2017-01-05 21:48:08]

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, 2017-01-06 01:40:00]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1483652855838670,
"parent_rev": "3d815ccd6917c759787784fd466a6beed97017f6", "commit_rev":
"7b1ab28d89a2ff18515b3c699dfc02a15aae84ee"}

[commit-bot: I haz the power, 2017-01-06 01:40:29]

Description was changed from

==========
Add test to check for crash caused by stale WebContents in
chrome://interstitials

BUG=611706
==========

to

==========
Add test to check for crash caused by stale WebContents in
chrome://interstitials

BUG=611706

Review-Url: https://codereview.chromium.org/2618573002
Cr-Commit-Position: refs/heads/master@{#441798}
Committed:
https://chromium.googlesource.com/chromium/src/+/7b1ab28d89a2ff18515b3c699dfc...
==========

[commit-bot: I haz the power, 2017-01-06 01:40:30]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/chromium/src/+/7b1ab28d89a2ff18515b3c699dfc...