[arm64] Fix AssertStackConsistency.

[arm64] Fix AssertStackConsistency.

The implementation temporarily modifies jssp to avoid needing a scratch
register, then restores it afterwards. However, the exception path
wasn't properly restoring the value.

With this patch, failures in this part of AssertStackConsistency get
reported properly (with backtrace and a BailoutReason).

BUG=

Committed: https://crrev.com/f7c7cb8fe4ff9d37cba4fcc4310bcf6a812eb060
Cr-Commit-Position: refs/heads/master@{#33135}

[jbramley, 2016-01-05 16:58:19]

jacob.bramley@arm.com changed reviewers:
+ ahaas@chromium.org, bmeurer@chromium.org, jarin@chromium.org

[Benedikt Meurer, 2016-01-05 18:10:57]

LGTM.

[jbramley, 2016-01-06 09:11:12]

The CQ bit was checked by jacob.bramley@arm.com

[commit-bot: I haz the power, 2016-01-06 09:11:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1556993004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1556993004/1

[commit-bot: I haz the power, 2016-01-06 09:43:34]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-01-06 09:43:53]

Description was changed from

==========
[arm64] Fix AssertStackConsistency.

The implementation temporarily modifies jssp to avoid needing a scratch
register, then restores it afterwards. However, the exception path
wasn't properly restoring the value.

With this patch, failures in this part of AssertStackConsistency get
reported properly (with backtrace and a BailoutReason).

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

to

==========
[arm64] Fix AssertStackConsistency.

The implementation temporarily modifies jssp to avoid needing a scratch
register, then restores it afterwards. However, the exception path
wasn't properly restoring the value.

With this patch, failures in this part of AssertStackConsistency get
reported properly (with backtrace and a BailoutReason).

BUG=

Committed: https://crrev.com/f7c7cb8fe4ff9d37cba4fcc4310bcf6a812eb060
Cr-Commit-Position: refs/heads/master@{#33135}
==========

[commit-bot: I haz the power, 2016-01-06 09:43:54]

Patchset 1 (id:??) landed as
https://crrev.com/f7c7cb8fe4ff9d37cba4fcc4310bcf6a812eb060
Cr-Commit-Position: refs/heads/master@{#33135}