Switch AppBannerManager on use of Unretained to use it's weakptr factory.

Switch AppBannerManager on use of Unretained to use it's weakptr factory.

It already uses the factory in one case, so using it here for consistency.

BUG=NONE

Committed: https://crrev.com/218a04b424934680f90aba877a97038673b4c39a
Cr-Commit-Position: refs/heads/master@{#317181}

[Ted C, 2015-02-19 22:17:55]

tedchoc@chromium.org changed reviewers:
+ dfalcantara@chromium.org

[Ted C, 2015-02-19 22:17:55]

PTAL

[gone, 2015-02-19 22:22:45]

lgtm

[Ted C, 2015-02-19 23:45:27]

New patchsets have been uploaded after l-g-t-m from dfalcantara@chromium.org

[Ted C, 2015-02-19 23:45:40]

The CQ bit was checked by tedchoc@chromium.org

[commit-bot: I haz the power, 2015-02-19 23:46:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/942633002/20001

[commit-bot: I haz the power, 2015-02-20 00:10:32]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-20 00:11:35]

Patchset 2 (id:??) landed as
https://crrev.com/218a04b424934680f90aba877a97038673b4c39a
Cr-Commit-Position: refs/heads/master@{#317181}