src/vs/platform/protocol/electron-main/protocolMainService.ts/ProtocolMainService/addValidFileRoot
class ProtocolMainService:	addValidFileRoot(root: string): IDisposable {

		// Pass to `normalize` because we later also do the
		// same for all paths to check against.
		const normalizedRoot = normalize(root);

		if (!this.validRoots.get(normalizedRoot)) {
			this.validRoots.set(normalizedRoot, true);

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

		return Disposable.None;
	}