Fix regression in Mac AX live region support

Fix regression in Mac AX live region support

As part of a refactoring, the code to detect if a new live region
was added was accidentally modified to trigger if a live region
was changed in any way. It should only trigger on a brand-new
live region.

BUG=469276
Committed: https://crrev.com/6f67a46b2822001d53d9df18d2f60b4f318c76e9
Cr-Commit-Position: refs/heads/master@{#322434}

[dmazzoni, 2015-03-26 17:27:47]

dmazzoni@chromium.org changed reviewers:
+ dtseng@chromium.org

[David Tseng, 2015-03-26 17:37:33]

lgtm

[dmazzoni, 2015-03-26 17:38:11]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2015-03-26 17:38:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1030373003/20001

[commit-bot: I haz the power, 2015-03-26 18:29:28]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-26 18:30:41]

Patchset 2 (id:??) landed as
https://crrev.com/6f67a46b2822001d53d9df18d2f60b4f318c76e9
Cr-Commit-Position: refs/heads/master@{#322434}