Polymer core-ajax不会发布JSON？

I'm using core-ajax to retrieve JSON data just fine. Turning the component around to post back to the server as JSON is another thing altogether. In all cases, and irrespective of the contentType or handleAs parameters passed in, it appears that my JSON object I'm passing in as an input is being converted back to key=value in the server headers.I'm using core-ajax to retrieve JSON data just