[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::didClose(
    WebPresentationConnectionCloseReason reason,
    const String& message) {
  if (m_state == WebPresentationConnectionState::Closed)
    return;

  m_state = WebPresentationConnectionState::Closed;
  dispatchStateChangeEvent(PresentationConnectionCloseEvent::create(
       EventTypeNames::close, connectionCloseReasonToString(reason), message));
 }

void PresentationConnection::didClose(
    WebPresentationConnectionCloseReason reason,
    const String& message) {
  if (m_state == WebPresentationConnectionState::Closed)
    return;

  m_state = WebPresentationConnectionState::Closed;
  dispatchStateChangeEvent(PresentationConnectionCloseEvent::create(
       EventTypeNames::close, connectionCloseReasonToString(reason), message));
 }
