[CrOS] Show extensions that can use file_handlers in Files app.

[CrOS] Show extensions that can use file_handlers in Files app.

An earlier CL enabled file_handlers and chrome.app.runtime to be used
by whitelisted extensions:
https://codereview.chromium.org/265503003

This updates the Files app to show these extensions as handlers.

BUG=329587
Committed: https://crrev.com/7ac54997a982364351f30c08a4f85f0bf821347a
Cr-Commit-Position: refs/heads/master@{#297367}

[jackhou1, 2014-09-30 03:17:34]

jackhou@chromium.org changed reviewers:
+ yoshiki@chromium.org

[jackhou1, 2014-09-30 03:17:34]

yoshiki, could you take a look?

[yoshiki, 2014-09-30 04:55:31]

lgtm

[jackhou1, 2014-09-30 04:57:13]

The CQ bit was checked by jackhou@chromium.org

[commit-bot: I haz the power, 2014-09-30 04:57:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/609643002/1

[commit-bot: I haz the power, 2014-09-30 05:10:29]

Committed patchset #1 (id:1) as d8392ad38ee1d59d6a4fcd41dac9ff8356585c26

[commit-bot: I haz the power, 2014-09-30 05:11:06]

Patchset 1 (id:??) landed as
https://crrev.com/7ac54997a982364351f30c08a4f85f0bf821347a
Cr-Commit-Position: refs/heads/master@{#297367}