ains(child)) {
          return true;
        }

        contentElements = Polymer.dom(element).querySelectorAll('content');

        for (contentIndex = 0; contentIndex < contentElements.length; ++contentIndex) {

          distributedNodes = Polymer.dom(contentElements[contentIndex]).getDistributedNodes();

          for (nodeIndex = 0; nodeIndex < distributedNodes.length; ++nodeIndex) {

            if (this._composedTreeContains(distributedNodes[nodeIndex], child)) {
              return true;
         