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It's now just calling ChangeListLoader::LoaderIfNeeded in exactly the
same list of arguments.

Along the way remove some unused forward references and #include.

BUG=none

Review URL: https://chromiumcodereview.appspot.com/14328038

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@195209 0039d316-1c4b-4281-b951-d872f2087c98