New SimpleCache Entry test for duplicate dooms.

New SimpleCache Entry test for duplicate dooms.

Adds a regression test for bug 317138. This test is interesting
because it generates exactly the same stacks that we're seeing in
crash reports on that bug. This is a good regression test, so I
suggest we land it, as well as look at it for more confidence that
our fix to bug 317138 is the right fix.

R=ttuttle@chromium.org,jkarlin@chromium.org
BUG=317138
Committed: https://crrev.com/219ac0b8461239768efa1cad3bca720bbaf065d1
Cr-Commit-Position: refs/heads/master@{#292399}

[gavinp, 2014-08-27 14:59:19]

ttuttle: PTAL.

jkarlin: FYI. Awesome discovery by you!!!

[Deprecated (see juliatuttle), 2014-08-28 13:53:51]

On 2014/08/27 14:59:19, gavinp wrote:
> ttuttle: PTAL.
> 
> jkarlin: FYI. Awesome discovery by you!!!

lgtm.

[gavinp, 2014-08-28 15:33:10]

The CQ bit was checked by gavinp@chromium.org

[commit-bot: I haz the power, 2014-08-28 15:33:53]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/gavinp@chromium.org/509973002/40001

[commit-bot: I haz the power, 2014-08-28 16:29:35]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_arm64_dbg_recipe on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_arm64_d...)

[commit-bot: I haz the power, 2014-08-28 16:48:38]

Committed patchset #3 (id:40001) as dc3ffa12e082ca7f21e411759f48b41007163cee

[commit-bot: I haz the power, 2014-09-10 03:00:07]

Patchset 3 (id:??) landed as
https://crrev.com/219ac0b8461239768efa1cad3bca720bbaf065d1
Cr-Commit-Position: refs/heads/master@{#292399}