Expose the ZoneSpecification print handler

[feinstein]

I currently have my app wrapped by a runZonedGuarded and wanted to wrap it instead with a Chain.capture to get full stack traces, but I can't because my app needs the ZoneSpecification print handler, which is not currently exposed by this package.

[lrhn]

As mentioned in the linked pull request, you can nest zones, so you don't need every zone-introducing function to allow a zone specification on top.

Just do:

Chain.capture(() => runZonedGuarded(zoneSpecification: ZoneSpecification(print: _handlePrint), () {
   // actual code
}))

or

runZonedGuarded(zoneSpecification: ZoneSpecification(print: _handlePrint), () => Chain.capture(() { 
   // actual code
}))

Either works, I doubt they'll step on each other's definitions.

The result is a zone which has all the handlers of their parent zones.

[feinstein]

@lrhn thanks for the clarification.