Fix a double-throw in JSReceiver::DefineProperties

Fix a double-throw in JSReceiver::DefineProperties

If ToObject() has thrown, do not throw another exception. The reason
this does not currently fail is that 1. Errors used to be created
through JS natives, and 2. the JSEntryStub clears any pending
exceptions. So, when calling into JS to create the new error, the old
exception was cleared.

BUG=5259
Committed: https://crrev.com/588eefef6d6eb04b6e19ed4bbb0b82dc5a601ccf
Cr-Commit-Position: refs/heads/master@{#38300}

[jgruber, 2016-08-03 13:50:22]

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

[commit-bot: I haz the power, 2016-08-03 13:50:27]

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

[jgruber, 2016-08-03 13:51:09]

jgruber@chromium.org changed reviewers:
+ jkummerow@chromium.org

[Jakob Kummerow, 2016-08-03 13:51:56]

lgtm

[commit-bot: I haz the power, 2016-08-03 14:32:31]

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

[commit-bot: I haz the power, 2016-08-03 14:32:32]

Dry run: This issue passed the CQ dry run.

[jgruber, 2016-08-03 14:37:58]

The CQ bit was checked by jgruber@chromium.org

[commit-bot: I haz the power, 2016-08-03 14:38:12]

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, 2016-08-03 14:39:53]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-03 14:43:34]

Description was changed from

==========
Fix a double-throw in JSReceiver::DefineProperties

If ToObject() has thrown, do not throw another exception. The reason
this does not currently fail is that 1. Errors used to be created
through JS natives, and 2. the JSEntryStub clears any pending
exceptions. So, when calling into JS to create the new error, the old
exception was cleared.

BUG=5259
==========

to

==========
Fix a double-throw in JSReceiver::DefineProperties

If ToObject() has thrown, do not throw another exception. The reason
this does not currently fail is that 1. Errors used to be created
through JS natives, and 2. the JSEntryStub clears any pending
exceptions. So, when calling into JS to create the new error, the old
exception was cleared.

BUG=5259

Committed: https://crrev.com/588eefef6d6eb04b6e19ed4bbb0b82dc5a601ccf
Cr-Commit-Position: refs/heads/master@{#38300}
==========

[commit-bot: I haz the power, 2016-08-03 14:43:35]

Patchset 1 (id:??) landed as
https://crrev.com/588eefef6d6eb04b6e19ed4bbb0b82dc5a601ccf
Cr-Commit-Position: refs/heads/master@{#38300}