Fix a hidden crash when ImeThread feature is used

Fix a hidden crash when ImeThread feature is used

DCHECK in PlainTextRange's constructor causes a crash when start > end, but
the test passes, probably because it's a renderer crash and we call it at
the end.

In this case, we'll swap start and end just like BaseInputConnection does.

Also adds some tests to fix the behavior and prevents a crash in the future.

BUG=

Committed: https://crrev.com/d7e40d40a011ad58385e8935764898bdde795aa2
Cr-Commit-Position: refs/heads/master@{#408927}

[Changwan Ryu, 2016-07-27 08:07:30]

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

[commit-bot: I haz the power, 2016-07-27 08:07:43]

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

[Changwan Ryu, 2016-07-27 08:08:20]

changwan@chromium.org changed reviewers:
+ aelias@chromium.org, yabinh@chromium.org

[Changwan Ryu, 2016-07-27 08:08:21]

I've encountered this while fixing something else. PTAL.

[commit-bot: I haz the power, 2016-07-27 08:55:21]

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

[commit-bot: I haz the power, 2016-07-27 08:55:22]

Dry run: This issue passed the CQ dry run.

[Changwan Ryu, 2016-08-01 05:36:52]

On 2016/07/27 08:08:21, Changwan Ryu wrote:
> I've encountered this while fixing something else. PTAL.

ping! A gentle reminder.

[yabinh, 2016-08-01 06:33:38]

lgtm

[Changwan Ryu, 2016-08-01 06:53:52]

The CQ bit was checked by changwan@chromium.org

[commit-bot: I haz the power, 2016-08-01 06:54:07]

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, 2016-08-01 07:57:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-01 08:00:12]

Description was changed from

==========
Fix a hidden crash when ImeThread feature is used

DCHECK in PlainTextRange's constructor causes a crash when start > end, but
the test passes, probably because it's a renderer crash and we call it at
the end.

In this case, we'll swap start and end just like BaseInputConnection does.

Also adds some tests to fix the behavior and prevents a crash in the future.

BUG=
==========

to

==========
Fix a hidden crash when ImeThread feature is used

DCHECK in PlainTextRange's constructor causes a crash when start > end, but
the test passes, probably because it's a renderer crash and we call it at
the end.

In this case, we'll swap start and end just like BaseInputConnection does.

Also adds some tests to fix the behavior and prevents a crash in the future.

BUG=

Committed: https://crrev.com/d7e40d40a011ad58385e8935764898bdde795aa2
Cr-Commit-Position: refs/heads/master@{#408927}
==========

[commit-bot: I haz the power, 2016-08-01 08:00:13]

Patchset 1 (id:??) landed as
https://crrev.com/d7e40d40a011ad58385e8935764898bdde795aa2
Cr-Commit-Position: refs/heads/master@{#408927}