@Override
  public void close() throws IOException {
    channelOpen.set(false);
    onEventComplete(Event.Close);
  }
Returns the value of the ambry specific content length header ({@link RestUtils.Headers#BLOB_SIZE}. If there is
no such header, returns length in the "Content-Length" header. If there is no such header, returns 0.
<p/>
This function does not individually count the bytes in the content (it is not possible) so the bytes received may
actually be different if the stream is buggy or the client made a mistake. Do *not* treat this as fully accurate.
@return the size of content as defined in headers. Might not be actual length of content if the stream is buggy.
ambry-test-utils/src/main/java/com/github/ambry/rest/MockRestRequest.java