src/vs/workbench/api/common/extHostTask.ts/ExtHostTaskBase/addCustomExecution
class ExtHostTaskBase:	protected async addCustomExecution(taskDTO: tasks.ITaskDTO, task: vscode.Task, isProvided: boolean): Promise<void> {
		const taskId = await this._proxy.$createTaskId(taskDTO);
		if (!isProvided && !this._providedCustomExecutions2.has(taskId)) {
			this._notProvidedCustomExecutions.add(taskId);
			// Also add to active executions when not coming from a provider to prevent timing issue.
			this._activeCustomExecutions2.set(taskId, <types.CustomExecution>task.execution);
		}
		this._providedCustomExecutions2.set(taskId, <types.CustomExecution>task.execution);
	}