[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}
bool PresentationConnection::canSendMessage(ExceptionState& exceptionState) {
  if (m_state != WebPresentationConnectionState::Connected) {
    throwPresentationDisconnectedError(exceptionState);
    return false;
  }

  return !!presentationClient(getExecutionContext());
}

bool PresentationConnection::canSendMessage(ExceptionState& exceptionState) {
  if (m_state != WebPresentationConnectionState::Connected) {
    throwPresentationDisconnectedError(exceptionState);
    return false;
  }

  return !!presentationClient(getExecutionContext());
}
