Properly determine if a new key was added in AesDecryptor::Update()

Properly determine if a new key was added in AesDecryptor::Update()

BUG=448219
TEST=new test passes

Committed: https://crrev.com/4d83add3219d80f900912f5f5d260f54a7952af1
Cr-Commit-Position: refs/heads/master@{#320958}

[jrummell, 2015-03-14 00:50:16]

jrummell@chromium.org changed reviewers:
+ ddorwin@chromium.org, sandersd@chromium.org

[jrummell, 2015-03-14 00:50:17]

PTAL

[sandersd (OOO until July 31), 2015-03-16 20:07:02]

lgtm

[jrummell, 2015-03-17 01:27:01]

The CQ bit was checked by jrummell@chromium.org

[commit-bot: I haz the power, 2015-03-17 01:27:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1002193005/1

[commit-bot: I haz the power, 2015-03-17 05:59:46]

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

[commit-bot: I haz the power, 2015-03-17 05:59:47]

Try jobs failed on following builders:
  linux_chromium_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[jrummell, 2015-03-17 18:16:33]

The CQ bit was checked by jrummell@chromium.org

[jrummell, 2015-03-17 18:16:33]

The patchset sent to the CQ was uploaded after l-g-t-m from
sandersd@chromium.org
Link to the patchset: https://codereview.chromium.org/1002193005/#ps20001
(title: "Fix pipeline test")

[commit-bot: I haz the power, 2015-03-17 18:16:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1002193005/20001

[commit-bot: I haz the power, 2015-03-17 19:43:37]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-17 19:44:34]

Patchset 2 (id:??) landed as
https://crrev.com/4d83add3219d80f900912f5f5d260f54a7952af1
Cr-Commit-Position: refs/heads/master@{#320958}