HTML5 FileSystem: How to revoke granted quota?

I use `window.webkitStorageInfo.requestQuota()` to get disk quota. Everything works as it should but I can't revoke already granted quota for debug purposes. Seems there is no API for that. And more over I can't find how it can be done through Chrome interface. I've found this link: `chrome://quota-internals/` but it just provides a read only info. I am developing chrome extension and even uninstalling/installing of it doesn't help. Who knows how to reset local disk storage settings for the site (or extension) or even the storage as a whole?