for helloworld example, 503/(failed) NET ERR_INVALID_HTTP_RESPONSE

I think envoy is proxy, it's ok when direct connect to 9090.

but error. 8080 is ok.

```javascript
var client = new GreeterClient('http://' + window.location.hostname + ':9090',
null, null);

```


Start with the helloworld example and the GreeterClient endpoint shown in the issue, comparing requests through port 9090 with the working port 8080 path. Reproduce the browser error and inspect the Envoy proxy path and configuration involved; done means the example works through the intended proxy endpoint without NET_ERR_INVALID_HTTP_RESPONSE.

Written by the indexing model from the issue text.