src/vs/platform/protocol/electron-main/protocolMainService.ts/ProtocolMainService/addValidFileRoot
class ProtocolMainService:	addValidFileRoot(root: URI): IDisposable {
		if (!this.validRoots.get(root)) {
			this.validRoots.set(root, true);

			return toDisposable(() => this.validRoots.delete(root));
		}

		return Disposable.None;
	}