Avoid mixed content when expanding context in code review tool

Avoid mixed content when expanding context in code review tool
https://bugs.webkit.org/show_bug.cgi?id=106060

Patch by James Robinson <jamesr@chromium.org> on 2013-01-03
Reviewed by Tony Chang.

Example failure: "The page at https://bugs.webkit.org/attachment.cgi?id=181222&action=review displayed insecure
content from http://svn.webkit.org/repository/webkit/trunk/Source/WebCore/page/EventHandler.cpp?p=138617." This
loads from "//svn.webkit.org/..." so the protocol matches.

* code-review.js:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@138768 268f45cc-cd09-0410-ab3c-d52691b4dbfc