Referrer Policy: Update SanitizeForRequest with new default behavior.

Referrer Policy: Update SanitizeForRequest with new default behavior.

Currently, we'll crash when this method is called if a site sets
`NoReferrerWhenDowngrade`. That seems like something worth fixing. :)

BUG=431711
Committed: https://crrev.com/3b0e841aa8b7d5ca5999f4340b8fa6f73305d3d2
Cr-Commit-Position: refs/heads/master@{#303629}

[Mike West, 2014-11-11 10:41:06]

mkwst@chromium.org changed reviewers:
+ jochen@chromium.org

[Mike West, 2014-11-11 10:41:06]

Jochen, WDYT?

[jochen (gone - plz use gerrit), 2014-11-11 10:45:28]

lgtm

[Mike West, 2014-11-11 10:49:16]

The CQ bit was checked by mkwst@chromium.org

[commit-bot: I haz the power, 2014-11-11 10:49:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/689363003/20001

[commit-bot: I haz the power, 2014-11-11 12:22:44]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2014-11-11 12:24:00]

Patchset 2 (id:??) landed as
https://crrev.com/3b0e841aa8b7d5ca5999f4340b8fa6f73305d3d2
Cr-Commit-Position: refs/heads/master@{#303629}

[Mike West, 2014-11-11 12:42:11]

A revert of this CL (patchset #2 id:20001) has been created in
https://codereview.chromium.org/683233003/ by mkwst@chromium.org.

The reason for reverting is: Doesn't compile on the debug bot. ?!.