Content verification: Don't fail on non-existence.

Content verification: Don't fail on non-existence.

This prevents content verification (when active) from disabling
an extension when the extension attempts to load a non-existent
resource in its own chrome-extension URL space.

BUG=404802
Committed: https://crrev.com/88d96e66d39684c2f8c9336042836dc90f4be85b
Cr-Commit-Position: refs/heads/master@{#292095}

[Ken Rockot(use gerrit already), 2014-08-27 01:34:36]

rockot@chromium.org changed reviewers:
+ yoz@chromium.org

[Ken Rockot(use gerrit already), 2014-08-27 01:34:36]

Yoyo could you please take a look? You have been chosen at random. How exciting!
AFAIK the only two people familiar with this code are Antony and myself.

[Yoyo Zhou, 2014-08-27 01:43:26]

I will have to randomly LGTM it then!

[Ken Rockot(use gerrit already), 2014-08-27 03:12:00]

The CQ bit was checked by rockot@chromium.org

[commit-bot: I haz the power, 2014-08-27 03:12:43]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/rockot@chromium.org/512573003/1

[commit-bot: I haz the power, 2014-08-27 04:26:40]

Committed patchset #1 (1) as bec2f2c3a36a6f82a7f3e6cec362c346ec14f9e0

[commit-bot: I haz the power, 2014-09-10 02:49:40]

Patchset 1 (id:??) landed as
https://crrev.com/88d96e66d39684c2f8c9336042836dc90f4be85b
Cr-Commit-Position: refs/heads/master@{#292095}