2011-01-31 Charlie Reis <creis@chromium.org>

      Reviewed by Mihai Parparita.

        Add sanity check to help diagnose bug 52819
        https://bugs.webkit.org/show_bug.cgi?id=53402

        Crash early if the children of fromItem look invalid.

        * loader/HistoryController.cpp:

git-svn-id: svn://svn.chromium.org/blink/trunk@77210 bbb929c8-8fbe-4397-9dbb-9b2b20218538