Create a new Isolate object with a restricted set of capabilities.
The port should be a control port for an isolate, as taken from
another Isolate object.
The capabilities should be the subset of the capabilities that are available to the original isolate. Capabilities of an isolate are locked to that isolate, and have no effect anywhere else, so the capabilities should come from the same isolate as the control port.
If all the available capabilities are included, there is no reason to create a new object, since the behavior is defined entirely by the control port and capabilities.
Source
Isolate(this.controlPort, {this.pauseCapability,
this.terminateCapability});