[Extensions UI Mac] Use frameAfterAnimation for extension action button opacity

[Extensions UI Mac] Use frameAfterAnimation for extension action button opacity

Button opacity for extension actions is set when the container frame changes,
but if the button is also animating, we need to use the final frame to determine
the proper opacity.

BUG=530820
Committed: https://crrev.com/1be03651d5e0ce01407e2863d860b698182ef17f
Cr-Commit-Position: refs/heads/master@{#348696}

[Devlin, 2015-09-14 19:48:47]

rdevlin.cronin@chromium.org changed reviewers:
+ avi@chromium.org

[Devlin, 2015-09-14 19:48:47]

Mind taking a quick look, Avi?

[Avi (use Gerrit), 2015-09-14 19:55:41]

lgtm

[Devlin, 2015-09-14 19:57:15]

The CQ bit was checked by rdevlin.cronin@chromium.org

[commit-bot: I haz the power, 2015-09-14 19:57:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1346443002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1346443002/1

[commit-bot: I haz the power, 2015-09-14 20:09:12]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-14 20:09:56]

Patchset 1 (id:??) landed as
https://crrev.com/1be03651d5e0ce01407e2863d860b698182ef17f
Cr-Commit-Position: refs/heads/master@{#348696}

[commit-bot: I haz the power, 2015-09-23 12:36:21]

Patchset 1 (id:??) landed as
https://crrev.com/1be03651d5e0ce01407e2863d860b698182ef17f
Cr-Commit-Position: refs/heads/master@{#348696}