Reviewed by Maciej.

        The WebArchiver needs all the subresources of a document to be accessible
        through the DocLoader, so we can't remove a CachedResource simultaneously
        from the global Cache and all DocLoaders, just because it needs to be 
        reloaded in one.

        Fixes rdar://problem/5044366

        * loader/Cache.cpp:
        (WebCore::Cache::remove):
           Don't evict the resource from all DocLoaders
        * manual-tests/test-iframes-loading-the-same-resource.html: Added.
           Alas it wasn't possible to make a nice layout test, even this manual test
           is not entirely deterministic



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@20511 268f45cc-cd09-0410-ab3c-d52691b4dbfc