Fix flaky FileFlusherTest.DuplicateRequests

Fix flaky FileFlusherTest.DuplicateRequests

The flakyness is cause by the racing that the first flush request
might be started before the duplicate request comes in.

Also fixed a problem that Job::ScheduleFinish could be called twice.
One from Cancel and the other from Start on a canceled job.

BUG=647070
Committed: https://crrev.com/f8838f1b9bbba7eacaf398da4eaaf9996727b502
Cr-Commit-Position: refs/heads/master@{#418914}

[xiyuan, 2016-09-15 17:49:14]

The CQ bit was checked by xiyuan@chromium.org to run a CQ dry run

[xiyuan, 2016-09-15 17:49:19]

xiyuan@chromium.org changed reviewers:
+ achuith@chromium.org

[commit-bot: I haz the power, 2016-09-15 17:50:05]

Dry run: 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, 2016-09-15 18:30:34]

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

[commit-bot: I haz the power, 2016-09-15 18:30:34]

Dry run: This issue passed the CQ dry run.

[achuithb, 2016-09-15 18:36:56]

lgtm

https://codereview.chromium.org/2342813003/diff/1/chrome/browser/chromeos/bas...
File chrome/browser/chromeos/base/file_flusher.cc (right):

https://codereview.chromium.org/2342813003/diff/1/chrome/browser/chromeos/bas...
chrome/browser/chromeos/base/file_flusher.cc:193:
DCHECK(std::none_of(jobs_.begin(), jobs_.end(),
Wow, nice. It's like python.

[xiyuan, 2016-09-15 18:38:11]

The CQ bit was checked by xiyuan@chromium.org

[commit-bot: I haz the power, 2016-09-15 18:38:39]

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, 2016-09-15 18:44:48]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-15 18:46:28]

Description was changed from

==========
Fix flaky FileFlusherTest.DuplicateRequests

The flakyness is cause by the racing that the first flush request
might be started before the duplicate request comes in.

Also fixed a problem that Job::ScheduleFinish could be called twice.
One from Cancel and the other from Start on a canceled job.

BUG=647070
==========

to

==========
Fix flaky FileFlusherTest.DuplicateRequests

The flakyness is cause by the racing that the first flush request
might be started before the duplicate request comes in.

Also fixed a problem that Job::ScheduleFinish could be called twice.
One from Cancel and the other from Start on a canceled job.

BUG=647070

Committed: https://crrev.com/f8838f1b9bbba7eacaf398da4eaaf9996727b502
Cr-Commit-Position: refs/heads/master@{#418914}
==========

[commit-bot: I haz the power, 2016-09-15 18:46:29]

Patchset 1 (id:??) landed as
https://crrev.com/f8838f1b9bbba7eacaf398da4eaaf9996727b502
Cr-Commit-Position: refs/heads/master@{#418914}