Fix flaky MojoDOMStorageBrowserTest

Fix flaky MojoDOMStorageBrowserTest

Rather than waiting for a connection to the database after the first part
of the test runs, make sure we're connected before starting the test.
This should make sure that all changes are actually flushed before the
browser shuts down.

BUG=692885
Review-Url: https://codereview.chromium.org/2700003002
Cr-Commit-Position: refs/heads/master@{#453745}
Committed: https://chromium.googlesource.com/chromium/src/+/8a7d571a3c9fbe2bac5d02a79848d2c188a264c0

[Marijn Kruisselbrink, 2017-02-17 19:57:55]

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

[commit-bot: I haz the power, 2017-02-17 19:58:57]

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, 2017-02-17 20:41:20]

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

[commit-bot: I haz the power, 2017-02-17 20:41:21]

Dry run: Try jobs failed on following builders:
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)

[Marijn Kruisselbrink, 2017-02-23 22:55:48]

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

[commit-bot: I haz the power, 2017-02-23 22:56:47]

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, 2017-02-23 23:51:26]

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

[commit-bot: I haz the power, 2017-02-23 23:51:27]

Dry run: This issue passed the CQ dry run.

[Marijn Kruisselbrink, 2017-02-28 21:30:06]

Description was changed from

==========
WIP try to fix test flakyness

BUG=692885
==========

to

==========
Fix flaky MojoDOMStorageBrowserTest

Rather than waiting for a connection to the database after the first part
of the test runs, make sure we're connected before starting the test.
This should make sure that all changes are actually flushed before the
browser shuts down.

BUG=692885
==========

[Marijn Kruisselbrink, 2017-02-28 21:30:17]

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

[commit-bot: I haz the power, 2017-02-28 21:30:52]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Marijn Kruisselbrink, 2017-02-28 21:53:26]

mek@chromium.org changed reviewers:
+ dmurph@chromium.org

[Marijn Kruisselbrink, 2017-02-28 21:53:27]

dmurph: want to review this? 

For background, if the first localstorage operation that is done during the
lifetime of a browser is a "clear()" (as is the case in this browser test), it
is possible for the javascript to write stuff to localstorage, and think it's
done, while the browser process isn't actually connected to leveldb yet. In such
a case if the browser shuts down there is a high likelihood of data getting
lost. This shouldn't effect real world situations really, as it's unlikely the
only origin using localstorage started out by doing clear(), and on top of that
the browser is immediately quit after javascript is done writing to storage. So
adding special code in the test like this to make sure things are actually
written seems a reasonable compromise.

(and this CL changes the special test logic to try to flush things from not just
waiting after the javascript code runs, but instead making sure the connection
from the browserprocess to leveldb exists before javascript code even runs,
thereby making sure that the flush at the end actually always flushes
everything).

[commit-bot: I haz the power, 2017-02-28 22:12:35]

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

[commit-bot: I haz the power, 2017-02-28 22:12:36]

Dry run: This issue passed the CQ dry run.

[dmurph, 2017-02-28 22:38:49]

lgtm

[dmurph, 2017-02-28 22:38:55]

The CQ bit was checked by dmurph@chromium.org

[commit-bot: I haz the power, 2017-02-28 22:39:35]

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, 2017-02-28 23:43:36]

CQ is committing da patch.

Bot data: {"patchset_id": 40001, "attempt_start_ts": 1488321535167890,
"parent_rev": "e4ac2e9a324a943abe94c8161273904c53bc02b3", "commit_rev":
"8a7d571a3c9fbe2bac5d02a79848d2c188a264c0"}

[commit-bot: I haz the power, 2017-02-28 23:44:20]

Description was changed from

==========
Fix flaky MojoDOMStorageBrowserTest

Rather than waiting for a connection to the database after the first part
of the test runs, make sure we're connected before starting the test.
This should make sure that all changes are actually flushed before the
browser shuts down.

BUG=692885
==========

to

==========
Fix flaky MojoDOMStorageBrowserTest

Rather than waiting for a connection to the database after the first part
of the test runs, make sure we're connected before starting the test.
This should make sure that all changes are actually flushed before the
browser shuts down.

BUG=692885

Review-Url: https://codereview.chromium.org/2700003002
Cr-Commit-Position: refs/heads/master@{#453745}
Committed:
https://chromium.googlesource.com/chromium/src/+/8a7d571a3c9fbe2bac5d02a79848...
==========

[commit-bot: I haz the power, 2017-02-28 23:44:20]

Committed patchset #3 (id:40001) as
https://chromium.googlesource.com/chromium/src/+/8a7d571a3c9fbe2bac5d02a79848...