<rdar://problem/5058714>
        http://bugs.webkit.org/show_bug.cgi?id=13050
        
        World leaks seen on Leopard after opening then closing tab (13050)

        Add a hash set to prevent the load count to be increased twice for the same resource.
        
        * WebCoreSupport/WebFrameLoaderClient.mm:
        (WebFrameLoaderClient::dispatchWillSendRequest):
        (WebFrameLoaderClient::dispatchDidFinishLoading):
        (WebFrameLoaderClient::dispatchDidFailLoading):
        * WebView/WebDocumentLoaderMac.h:
        * WebView/WebDocumentLoaderMac.mm:
        (loadingResources):
        (WebDocumentLoaderMac::increaseLoadCount):
        (WebDocumentLoaderMac::decreaseLoadCount):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@20195 268f45cc-cd09-0410-ab3c-d52691b4dbfc