Skip displaying zoom levels for scheme and host zoom changes.

Skip displaying zoom levels for scheme and host zoom changes.

Currently, ContentSettingsHandler::UpdateZoomLevelsExceptionsView(),
skips setting the origin for scheme and host zoom changes, but still
adds an entry to be displayed in the content settings page. This causes
an entry to be displayed with an origin of undefined. This CL changes
UpdateZoomLevelsExceptionsView() to skip adding an entry altogether.

BUG=453234
Committed: https://crrev.com/ed24b27948c5c04dadfb27b731129da6549e4459
Cr-Commit-Position: refs/heads/master@{#313839}

[Sam McNally, 2015-01-29 23:17:38]

sammc@chromium.org changed reviewers:
+ dbeam@chromium.org

[Dan Beam, 2015-01-30 00:29:14]

lgtm

[Sam McNally, 2015-01-30 00:29:39]

The CQ bit was checked by sammc@chromium.org

[commit-bot: I haz the power, 2015-01-30 00:30:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/883353003/1

[commit-bot: I haz the power, 2015-01-30 00:34:29]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-30 00:35:49]

Patchset 1 (id:??) landed as
https://crrev.com/ed24b27948c5c04dadfb27b731129da6549e4459
Cr-Commit-Position: refs/heads/master@{#313839}