src/vs/workbench/contrib/tasks/common/problemCollectors.ts/AbstractProblemCollector/processLine
class AbstractProblemCollector:	public processLine(line: string) {
		if (this.tail) {
			const oldTail = this.tail;
			this.tail = oldTail.then(() => {
				return this.processLineInternal(line);
			});
		} else {
			this.tail = this.processLineInternal(line);
		}
	}