src/vs/workbench/contrib/tasks/common/taskConfiguration.ts/from
	export function from(config: ExternalTaskRunnerConfiguration): Tasks.ExecutionEngine {
		let runner = config.runner || config._runner;
		let result: Tasks.ExecutionEngine | undefined;
		if (runner) {
			switch (runner) {
				case 'terminal':
					result = Tasks.ExecutionEngine.Terminal;
					break;
				case 'process':
					result = Tasks.ExecutionEngine.Process;
					break;
			}
		}
		let schemaVersion = JsonSchemaVersion.from(config);
		if (schemaVersion === Tasks.JsonSchemaVersion.V0_1_0) {
			return result || Tasks.ExecutionEngine.Process;
		} else if (schemaVersion === Tasks.JsonSchemaVersion.V2_0_0) {
			return Tasks.ExecutionEngine.Terminal;
		} else {
			throw new Error('Shouldn\'t happen.');
		}
	}