[arm64] Add assertions to Claim and Drop.

[arm64] Add assertions to Claim and Drop.

In particular, Claim doesn't work with a negative size, so ensure that
it is positive.

BUG=

Committed: https://crrev.com/4938aca2c27134c79926d2a6c093ebf658f8fbf3
Cr-Commit-Position: refs/heads/master@{#33198}

[jbramley, 2016-01-07 15:47:59]

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

[jbramley, 2016-01-07 15:48:00]

This would have caught the problem in
https://codereview.chromium.org/1537903004/ slightly earlier.

[Benedikt Meurer, 2016-01-08 06:22:40]

lgtm

[jbramley, 2016-01-11 10:02:38]

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

[commit-bot: I haz the power, 2016-01-11 10:02:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1565193002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1565193002/1

[commit-bot: I haz the power, 2016-01-11 10:26:13]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-01-11 10:27:11]

Description was changed from

==========
[arm64] Add assertions to Claim and Drop.

In particular, Claim doesn't work with a negative size, so ensure that
it is positive.

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

to

==========
[arm64] Add assertions to Claim and Drop.

In particular, Claim doesn't work with a negative size, so ensure that
it is positive.

BUG=

Committed: https://crrev.com/4938aca2c27134c79926d2a6c093ebf658f8fbf3
Cr-Commit-Position: refs/heads/master@{#33198}
==========

[commit-bot: I haz the power, 2016-01-11 10:27:11]

Patchset 1 (id:??) landed as
https://crrev.com/4938aca2c27134c79926d2a6c093ebf658f8fbf3
Cr-Commit-Position: refs/heads/master@{#33198}