- fix http://bugzilla.opendarwin.org/show_bug.cgi?id=4395
         REGRESSION: document.open doesn't clear the document

        Test: fast/dom/Document/document-reopen.html
        Test: fast/dom/Document/doc-open-while-parsing.html

        * dom/DocumentImpl.cpp:
        (WebCore::DocumentImpl::open): Only ignore open() while the frame is still loading the main resource.
        * page/Frame.cpp:
        (WebCore::Frame::isComplete): Added const specifier.
        (WebCore::Frame::isLoadingMainResource): New function.
        * page/Frame.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@13324 268f45cc-cd09-0410-ab3c-d52691b4dbfc