TimelineTask constructor
Create a task. The task ID will be set by the system.
If parent
is provided, the parent's task ID is provided as argument
'parentId' when start is called. In DevTools, this argument will result
in this TimelineTask being linked to the parent
TimelineTask.
Implementation
TimelineTask({TimelineTask parent})
: _parent = parent,
_taskId = _getNextAsyncId() {}