[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}
DEFINE_TRACE(PresentationConnection) {
  visitor->trace(m_blobLoader);
  visitor->trace(m_messages);
  EventTargetWithInlineData::trace(visitor);
  ContextClient::trace(visitor);
}

DEFINE_TRACE(PresentationConnection) {
  visitor->trace(m_blobLoader);
  visitor->trace(m_messages);
  EventTargetWithInlineData::trace(visitor);
  ContextClient::trace(visitor);
}
