connectionFactory property
The app's own connectionFactory, composed with connect timing instead of
being replaced by it.
HttpClient.connectionFactory is set-only, so a factory installed inside
previous's createHttpClient cannot be read back and preserved. Pass it
here and it keeps doing the connecting; only the combined connect phase
is then reported (see applyInstrumentedConnectionFactory). Leave it null
and any factory the prior overrides installed is replaced.
Implementation
final HttpConnectionFactory? connectionFactory;