Plugin Placeholders: Fix "blank first menu item" bug when no mime type.

Plugin Placeholders: Fix "blank first menu item" bug when no mime type.

When the plugin params don't include a MIME type, and there is no
plugin found, the first menu item will be blank.

This patch just removes the first menu item if there is no mime type.

BUG=354197
Committed: https://crrev.com/c2710e616b5fed15b8ae832a133f5419cfff2e39
Cr-Commit-Position: refs/heads/master@{#316903}

[tommycli, 2015-02-18 19:53:07]

tommycli@chromium.org changed reviewers:
+ bauerb@chromium.org

[tommycli, 2015-02-18 19:53:38]

Hi Bernhard,

PTAL.

This patch fixes the 'blank first menu item' bug. See
http://www.w3schools.com/html/tryit.asp?filename=tryhtml_object_plugin on a
plain-Chromium build to repro.

[Bernhard Bauer, 2015-02-18 21:03:36]

lgtm

[tommycli, 2015-02-18 21:13:53]

The CQ bit was checked by tommycli@chromium.org

[commit-bot: I haz the power, 2015-02-18 21:14:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/937823002/1

[commit-bot: I haz the power, 2015-02-18 22:33:02]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-18 22:33:46]

Patchset 1 (id:??) landed as
https://crrev.com/c2710e616b5fed15b8ae832a133f5419cfff2e39
Cr-Commit-Position: refs/heads/master@{#316903}