Register chrome-extension as a secure scheme so that adding resources from an extension doesn't trip the mixed content sensor.
Register chrome-extension as a secure scheme so that adding resources from an
extension doesn't trip the mixed content sensor.

BUG=35245

Review URL: http://codereview.chromium.org/840006

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@41531 0039d316-1c4b-4281-b951-d872f2087c98

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