Fix compile: remove an unnecessary call to WebHistoryItem::setOriginalURLString

That function had been a no-op for a while and was finally deleted in r169051.

BUG=none
TBR=abarth,arv

Review URL: https://codereview.chromium.org/197073006

git-svn-id: svn://svn.chromium.org/blink/trunk@169057 bbb929c8-8fbe-4397-9dbb-9b2b20218538