Test cases added: none, method rename

        Part of fix for <rdar://problem/4237479> REGRESSION (Cambridge-Denver): old QuickTime movie continues to play sound after reload

        * kwq/WebCoreBridge.h:
        * kwq/WebCoreBridge.mm:
        (-[WebCoreBridge handleFallbackContent]):
        Renamed bridge method mainResourceError to handleFallbackContent, since there are some
        main resource errors for which we should not render fallback content.  E.G user cancels
        and the cancel we do to prevent loading plugin content twice (see <rdar://problem/4258008>)


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@10536 268f45cc-cd09-0410-ab3c-d52691b4dbfc