CoreSession leak due to long time stored references in publication trees

    @Override
    public PublicationTree getPublicationTree(String treeName,
            CoreSession coreSession, Map<String, String> params,
            DocumentModel currentDocument) throws ClientException,
            PublicationTreeNotAvailable {
        PublicationTree tree = getOrBuildTree(treeName, coreSession, params);
        if (tree == null) {
            return null;
        }
        if (currentDocument != null) {
            tree.setCurrentDocument(currentDocument);
        }
        return new ProxyTree(tree, tree.getSessionId());
    }

    protected PublicationTree getOrBuildTree(String treeConfigName,
            CoreSession coreSession, Map<String, String> params)
            throws PublicationTreeNotAvailable {
        String key = computeTreeSessionId(treeConfigName, coreSession);
        PublicationTree tree;
        if (liveTrees.containsKey(key)) {
            tree = liveTrees.get(key);
        } else {
            tree = buildTree(key, treeConfigName, coreSession, params);
            if (tree != null) {
                liveTrees.put(key, tree);
            }
        }
        return tree;
    }

    protected PublicationTree buildTree(String sid, String treeConfigName,
            CoreSession coreSession, Map<String, String> params)
            throws PublicationTreeNotAvailable {
        try {
            PublicationTreeConfigDescriptor config = getPublicationTreeConfigDescriptor(treeConfigName);
            Map<String, String> allParameters = computeAllParameters(config,
                    params);
            PublicationTreeDescriptor treeDescriptor = getPublicationTreeDescriptor(config);
            PublishedDocumentFactory publishedDocumentFactory = getPublishedDocumentFactory(
                    config, treeDescriptor, coreSession, allParameters);
            return getPublicationTree(treeDescriptor, sid, coreSession,
                    allParameters, publishedDocumentFactory, config.getName(),
                    config.getTitle());
        } catch (PublisherException e) {
            log.error("Unable to build PublicationTree", e);
            return null;
        }
    }

  <extension
    target="org.nuxeo.ecm.platform.publisher.impl.service.PublisherServiceImpl"
    point="tree">

    <documentation>
      PublicationTree that allows retrieving all the published Rendition documents
      in addition to the 'standard' proxies for the given document.
    </documentation>
    <publicationTree name="RenditionPublicationCoreTree"
      class="org.nuxeo.ecm.platform.rendition.publisher.RenditionPublicationCoreTree" />

  </extension>