Clean up and deflake history navigation test

Clean up and deflake history navigation test

When returning from having navigated to navigate-back.html, both
runSecondStageOfTest() and the popstate event handler would set a
timeout that called history.back().  The first navigation would
trigger the hashchange event handler that signaled a pass, the
second ought to have had no effect.

In practice, the test occasionally timed out or crashed instead,
for unknown reasons.  Removing the extra history.back() timeout
apparently avoids this.

BUG=339265
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166325

[Jens Widell, 2014-01-30 13:32:39]

Please have a look.

Related to https://codereview.chromium.org/136463002/.

Without this change, I could reproduce crashes in debug and timeouts in release
rather easily by running "run-webkit-tests --repeat-each=N" with a sufficiently
high N.  One crash every hundred runs or so in debug and one timeout every
couple of thousand runs in release.

With this change, I had no failures after 10000 runs in debug and 60000 runs in
release.

[arv (Not doing code reviews), 2014-02-01 00:55:35]

LGTM

[Jens Widell, 2014-02-03 07:36:28]

On 2014/02/01 00:55:35, arv wrote:
> LGTM

Thanks!

In the meantime, a CL landed that marked the test as flaky in
LayoutTests/TestExpectations.  I updated this patch to revert that.  Is that
proper?  Or should this fix land, and TestExpectations be updated once the test
has proven not flaky?

[Jens Widell, 2014-02-03 18:06:07]

The CQ bit was checked by jl@opera.com

[commit-bot: I haz the power, 2014-02-03 18:06:36]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jl@opera.com/148453014/30001

[commit-bot: I haz the power, 2014-02-03 19:36:51]

Change committed as 166325

[commit-bot: I haz the power, 2014-02-03 19:36:57]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-02-03 19:36:58]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-02-03 19:37:26]

CQ bit was unchecked on CL. Ignoring.