[ash/shelf] ResourceBundle should be used as pointer not non-const ref

Modifying the code to retrieve a pointer rather than a non-const reference in ash/shelf module.

ResourceBundle::GetSharedInstance() returns a non-const reference, but it will
be changed to return a pointer, so updating the code to use it as a pointer

BUG=289640
Committed: https://crrev.com/668c3a429ee911ac96d7b4a4f8eefdbdc9f0abe3
Cr-Commit-Position: refs/heads/master@{#328334}

[anujsharma, 2015-05-05 14:13:13]

anujk.sharma@samsung.com changed reviewers:
+ skuhne@chromium.org

[anujsharma, 2015-05-05 14:13:14]

PTAL

[Mr4D (OOO till 08-26), 2015-05-05 14:22:25]

lgtm

[anujsharma, 2015-05-05 14:22:55]

On 2015/05/05 14:22:25, Mr4D wrote:
> lgtm

Thanks Mr4D for lgtm.

[anujsharma, 2015-05-05 14:22:59]

The CQ bit was checked by anujk.sharma@samsung.com

[commit-bot: I haz the power, 2015-05-05 14:23:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1119983006/1

[commit-bot: I haz the power, 2015-05-05 15:32:31]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-05 15:33:33]

Patchset 1 (id:??) landed as
https://crrev.com/668c3a429ee911ac96d7b4a4f8eefdbdc9f0abe3
Cr-Commit-Position: refs/heads/master@{#328334}