Remove unused WebHistoryItem::setReferrer() method
Remove unused WebHistoryItem::setReferrer() method

BUG=334125
R=marja@chromium.org

Review URL: https://codereview.chromium.org/150173002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@166138 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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