[Presentation API] Add layout test for connection.close() and fix test failures

Add layout test.

1-UA connection.close() hits NOTREACHED() in PresentationConnection::didChangeState(). Use PresentationConnection::didClose() instead.

BUG=697719

Review-Url: https://codereview.chromium.org/2730123003
Cr-Commit-Position: refs/heads/master@{#455225}
void PresentationConnection::didReceiveTextMessage(const WebString& message) {
  if (m_state != WebPresentationConnectionState::Connected)
    return;

  dispatchEvent(MessageEvent::create(message));
}

void PresentationConnection::didReceiveTextMessage(const WebString& message) {
  if (m_state != WebPresentationConnectionState::Connected)
    return;

  dispatchEvent(MessageEvent::create(message));
}
