src/vs/workbench/services/workingCopy/common/fileWorkingCopyManager.ts/FileWorkingCopyManager/workingCopies
class FileWorkingCopyManager:	get workingCopies(): (IUntitledFileWorkingCopy<U> | IStoredFileWorkingCopy<S>)[] {
		return [...this.stored.workingCopies, ...this.untitled.workingCopies];
	}