- <rdar://problem/5457865> REGRESSION (9A527): Safari crashes when opening a page
          that immediately redirects to a PDF

        I don't know how to make an automated test that trips over this.

        The immediate cause of this regression was making a back/forward list entry in
        this case. Earlier, the quick redirect would not results in a separate entry.
        That's possibly a bug too, but it's better to fix the crash first.

        The page cache was putting the document into a strange state: Still attached but
        with the renderer set to 0. There was no good reason to do this, so got rid of it.
        Moved the responsibility to the caller of not calling detach() when moving into
        the page cache. This is more of a frame loader thing than a document thing.

        * dom/Document.cpp: (WebCore::Document::detach): Added assertions that this is
        only called on a document that's attached and not in the page cache. Also moved
        the call to willRemove in here, so that callers can't make the mistake of not
        calling that function. Removed the incorrectly-positioned code that made this
        function do less if it was called on a document in the page cache.

        * history/CachedPage.cpp: (WebCore::CachedPage::clear): Removed the code to handle
        a document with a renderer of 0. There was no need to put the document into this
        state. Any document in the page cache will always be "attached".

        * loader/FrameLoader.cpp: (WebCore::FrameLoader::clear): Added a check to prevent
        from calling an unnecessary cancelParsing() on a document that's in the page cache
        and guard the call to detach() with a check of attached(), like all other calls to
        detach() on DOM objects.

        * page/Frame.cpp:
        (WebCore::Frame::setView): Added a missing check of attached(), like all other
        calls to detach() on DOM objects. Also added code to not call detach() on the
        document when it's in the page cache.
        (WebCore::Frame::setDocument): This call site already had the attached() check,
        but was missing the page cache check.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@25395 268f45cc-cd09-0410-ab3c-d52691b4dbfc