[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 PresentationConnectionProxy::OnClose() {
   DCHECK(target_connection_ptr_);
  source_connection_->didClose();
   target_connection_ptr_->DidChangeState(
       content::PRESENTATION_CONNECTION_STATE_CLOSED);
 }

 void PresentationConnectionProxy::OnClose() {
   DCHECK(target_connection_ptr_);
  source_connection_->didChangeState(
      blink::WebPresentationConnectionState::Closed);
   target_connection_ptr_->DidChangeState(
       content::PRESENTATION_CONNECTION_STATE_CLOSED);
 }
