Reland https://codereview.chromium.org/1271593002/ which was reverted

Reland https://codereview.chromium.org/1271593002/ which was reverted
in https://codereview.chromium.org/1273813005/. The CL is unchanged,
except the DCHECKs that uncovered another bug have been removed. They'll
be added back once that bug is fixed.

Fix cancellation of a pair of URLRequestJob subclasses.

URLRequestSimpleJob and URLRequestChromeJob can call back into their
parent URLRequestJob class after Kill() has been invoked, which can
cause Bad Things.

Longer term, we should think about the interface between URLRequestJob
and its subclasses, to see if we can create a more robust interface.

BUG=508900
Committed: https://crrev.com/363ce98af274c07f43acac74b7ca7c23641c996e
Cr-Commit-Position: refs/heads/master@{#342211}

Committed: https://crrev.com/fe5b536aa72231ffaa1f80b2f419beacdaf5d338
Cr-Commit-Position: refs/heads/master@{#342390}

[mmenke, 2015-08-07 15:29:24]

mmenke@chromium.org changed reviewers:
+ davidben@chromium.org

[mmenke, 2015-08-07 15:29:24]

Unlike the my partial reland from yesterday, this patch is identical to its
predecessor, except for removing the DCHECKs it added in URLRequestJob.

Looks like ServiceWorker may be the real culprit, this time.

[davidben, 2015-08-07 15:41:02]

On 2015/08/07 15:29:24, mmenke wrote:
> Looks like ServiceWorker may be the real culprit, this time.

I'm shocked, just *shocked*. :-)

[mmenke, 2015-08-07 15:43:34]

On 2015/08/07 15:41:02, David Benjamin wrote:
> On 2015/08/07 15:29:24, mmenke wrote:
> > Looks like ServiceWorker may be the real culprit, this time.
> 
> I'm shocked, just *shocked*. :-)

Given that we have classes written by the network stack team that have similar
issues, hard to completely blame this on ServiceWorker.  At least they have
tests that actually run their buggy codepath, though those test normally
pass....

[davidben, 2015-08-07 15:43:59]

lgtm. Gave this mostly just a cursory review as it's the same as the previous
CL, but for the DCHECKs.

[mmenke, 2015-08-07 15:45:53]

On 2015/08/07 15:43:59, David Benjamin wrote:
> lgtm. Gave this mostly just a cursory review as it's the same as the previous
> CL, but for the DCHECKs.

Thanks!  (And yea, don't think this need a full re-review)

[mmenke, 2015-08-07 15:45:56]

The CQ bit was checked by mmenke@chromium.org

[commit-bot: I haz the power, 2015-08-07 15:46:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1281943002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1281943002/1

[commit-bot: I haz the power, 2015-08-07 17:48:19]

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

[commit-bot: I haz the power, 2015-08-07 17:48:20]

Try jobs failed on following builders:
  win_chromium_x64_rel_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[mmenke, 2015-08-07 17:49:12]

The CQ bit was checked by mmenke@chromium.org

[commit-bot: I haz the power, 2015-08-07 17:49:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1281943002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1281943002/1

[commit-bot: I haz the power, 2015-08-07 18:34:56]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-07 18:35:37]

Patchset 1 (id:??) landed as
https://crrev.com/fe5b536aa72231ffaa1f80b2f419beacdaf5d338
Cr-Commit-Position: refs/heads/master@{#342390}