Reviewed by Darin.

        - fix http://bugs.webkit.org/show_bug.cgi?id=9952
          REGRESSION: Repro crash when dragging an image from the window to the address bar

        * page/FrameView.cpp:
        (WebCore::FrameView::~FrameView): Removed the call to Document::detach(). If this
        view is the current view, then the Frame should have already detached the document.
        Added an assertion that this is the case. If this view is not the current view,
        then it cannot access its document, but the page cache should have detached it already.
        Similarly, changed to call RenderPart::setWidget() only if this is the current view
        in the frame.
        (WebCore::FrameView::adjustViewSize): Added an assertion that this view is the current
        view in the frame.
        (WebCore::FrameView::layout): Ditto.
        (WebCore::FrameView::scheduleRelayout): Ditto.
        (WebCore::FrameView::scheduleRelayoutOfSubtree): Ditto.
        (WebCore::FrameView::windowClipRect): Ditto.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@18965 268f45cc-cd09-0410-ab3c-d52691b4dbfc