- fix crash on back/forward - reattach WebDocumentLoadState to data source when needed

        * WebView/WebDataSource.m:
        (-[WebDataSource _setWebFrame:]):
        (-[WebDataSource _initWithDocumentLoadState:]):
        * WebView/WebDataSourceInternal.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@16709 268f45cc-cd09-0410-ab3c-d52691b4dbfc