JMC wants to "dump default recording", which in JFR.next means dump all recording data,
and we should do this by dumping the special recording id 0.

When I do this from the JMC MBean browser I get:
Failed to execute 'openStream( 0 )'

 java.io.IOException: No recording data available
at jdk.management.jfr.FlightRecorderMXBeanImpl.openStream(jdk.management.jfr@9-ea/FlightRecorderMXBeanImpl.java:139)


Looking at the JFR code with Erik, it looked likely that this is because there are no complete chunks found in the call to makeChunkList() from PlatformRecorder.open().

The normal dump recording actions we do clones a new stopped recording.