Remove handling of invalid but non-empty main_frame_url.

Remove handling of invalid but non-empty main_frame_url.

It has been proven (via a live UMA experiment under "SBOffDomainInclusion.InvalidMainFrameURL")
to never happen in off-domain inclusion analysis.

BUG=412468
Committed: https://crrev.com/0e7f9e80ae5fc4f6af980eea1a8da12792cf95ff
Cr-Commit-Position: refs/heads/master@{#313915}

[gab, 2015-01-20 18:59:47]

gab@chromium.org changed reviewers:
+ grt@chromium.org

[gab, 2015-01-20 18:59:47]

Greg, PTAL, this is based on https://codereview.chromium.org/859903002/

Thanks,
Gab

[grt (UTC plus 2), 2015-01-21 02:05:10]

lgtm

[gab, 2015-01-30 12:44:27]

The CQ bit was checked by gab@chromium.org

[commit-bot: I haz the power, 2015-01-30 12:44:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/789613008/1

[commit-bot: I haz the power, 2015-01-30 12:46:54]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-01-30 12:46:55]

Try jobs failed on following builders:
  ios_rel_device_ninja_ng on tryserver.chromium.mac
(http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_rel_device_ni...)

[gab, 2015-01-30 13:31:51]

The CQ bit was checked by gab@chromium.org

[commit-bot: I haz the power, 2015-01-30 13:32:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/789613008/20001

[commit-bot: I haz the power, 2015-01-30 14:45:46]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-01-30 14:47:00]

Patchset 2 (id:??) landed as
https://crrev.com/0e7f9e80ae5fc4f6af980eea1a8da12792cf95ff
Cr-Commit-Position: refs/heads/master@{#313915}