Use WebFrame::setIsolatedWorldSecurityOrigin to allow cross-origin XHRs in content scripts.

http://trac.webkit.org/changeset/87423 adds the ability to associated a security origin with
an isolated world. Use that to make content script isolated worlds use the extension's
origin, and whitelist that origin in the page's renderer process for the host permissions
in the manifest.

BUG=18857
TEST=no
R=mpcomplete@chromium.org

Review URL: http://codereview.chromium.org/7071025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@87114 0039d316-1c4b-4281-b951-d872f2087c98
11 files changed