Don't update primary color if brand color is not enabled

Don't update primary color if brand color is not enabled

We always update the model refreshSelectedTab, but that should not
end up making any visual updates. In onPrimaryColorChanged we should
be checking the model for isUsingBrandColor.

BUG=497241
Committed: https://crrev.com/ca0908a1dab9f9cb6081e5106698ed4caa7e9127
Cr-Commit-Position: refs/heads/master@{#333101}

[Yusuf, 2015-06-05 17:52:01]

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

[Ted C, 2015-06-05 18:05:57]

lgtm

[Yusuf, 2015-06-05 18:08:39]

The CQ bit was checked by yusufo@chromium.org

[commit-bot: I haz the power, 2015-06-05 18:09:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1148323009/1

[commit-bot: I haz the power, 2015-06-05 18:38:07]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-05 19:06:18]

Patchset 1 (id:??) landed as
https://crrev.com/ca0908a1dab9f9cb6081e5106698ed4caa7e9127
Cr-Commit-Position: refs/heads/master@{#333101}