[Extensions] Fix override urls' visible urls

[Extensions] Fix override urls' visible urls

When we override a URL like chrome://bookmarks by an extension, it maps it to
the chrome-extension:// url, but should still display the chrome://bookmarks
url in the omnibox.  crrev.com/5fafa5aa3c2bde50f4f50511f134192147f86b55 changed
the way prefs were read, so it broke this.  Fix the breakage, and add a unittest
so that it doesn't happen again.

BUG=579389
Committed: https://crrev.com/2b7cf6ac0c8e1d6167a4925538fd11f41e1e0501
Cr-Commit-Position: refs/heads/master@{#371824}

[Devlin, 2016-01-25 21:53:26]

Patchset #1 (id:1) has been deleted

[Devlin, 2016-01-25 21:54:50]

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

[Devlin, 2016-01-25 21:54:51]

grr...there were no tests for the reverse lookup. :(

(Now there are, though!)

[Finnur, 2016-01-27 17:11:15]

Missed this yesterday. LGTM.

[Devlin, 2016-01-27 17:21:01]

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

[commit-bot: I haz the power, 2016-01-27 17:22:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1635663002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1635663002/20001

[commit-bot: I haz the power, 2016-01-27 18:23:59]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2016-01-27 18:25:09]

Description was changed from

==========
[Extensions] Fix override urls' visible urls

When we override a URL like chrome://bookmarks by an extension, it maps it to
the chrome-extension:// url, but should still display the chrome://bookmarks
url in the omnibox.  crrev.com/5fafa5aa3c2bde50f4f50511f134192147f86b55 changed
the way prefs were read, so it broke this.  Fix the breakage, and add a unittest
so that it doesn't happen again.

BUG=579389
==========

to

==========
[Extensions] Fix override urls' visible urls

When we override a URL like chrome://bookmarks by an extension, it maps it to
the chrome-extension:// url, but should still display the chrome://bookmarks
url in the omnibox.  crrev.com/5fafa5aa3c2bde50f4f50511f134192147f86b55 changed
the way prefs were read, so it broke this.  Fix the breakage, and add a unittest
so that it doesn't happen again.

BUG=579389

Committed: https://crrev.com/2b7cf6ac0c8e1d6167a4925538fd11f41e1e0501
Cr-Commit-Position: refs/heads/master@{#371824}
==========

[commit-bot: I haz the power, 2016-01-27 18:25:09]

Patchset 1 (id:??) landed as
https://crrev.com/2b7cf6ac0c8e1d6167a4925538fd11f41e1e0501
Cr-Commit-Position: refs/heads/master@{#371824}