Remove support for custom menu items in context menus.

Remove support for custom menu items in context menus.

Custom menu items where used for WebUI NTP and is no longer used.
This CL removes support for such menus.

BUG=None

Committed: https://crrev.com/b7931b4dec4529327e5c3a51bf59ece6a39e0dbe
Cr-Commit-Position: refs/heads/master@{#330412}

[aurimas (slooooooooow), 2015-05-18 18:42:46]

aurimas@chromium.org changed reviewers:
+ newt@chromium.org

[aurimas (slooooooooow), 2015-05-18 18:42:46]

PTAL

[newt (away), 2015-05-18 18:53:15]

lgtm

[aurimas (slooooooooow), 2015-05-18 18:55:04]

The CQ bit was checked by aurimas@chromium.org

[commit-bot: I haz the power, 2015-05-18 18:55:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1142863002/1

[aurimas (slooooooooow), 2015-05-18 20:23:34]

The CQ bit was unchecked by aurimas@chromium.org

[aurimas (slooooooooow), 2015-05-18 20:23:57]

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

[aurimas (slooooooooow), 2015-05-18 20:23:57]

tedchoc: PTAL at chrome/browser/ui/android/*

[Ted C, 2015-05-18 20:35:47]

lgtm

[aurimas (slooooooooow), 2015-05-18 20:42:43]

The CQ bit was checked by aurimas@chromium.org

[commit-bot: I haz the power, 2015-05-18 20:44:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1142863002/1

[commit-bot: I haz the power, 2015-05-18 20:50:39]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-18 22:42:55]

Patchset 1 (id:??) landed as
https://crrev.com/b7931b4dec4529327e5c3a51bf59ece6a39e0dbe
Cr-Commit-Position: refs/heads/master@{#330412}