Saving PlayerPrefs in Google Chrome NaCl

I'm having an issue where the PlayerPrefs won't save when I build my game for NaCl. It saves fine when I make a build for anything else (Android, Web Player, Desktop, etc). This happens when I upload an unpacked extension in developer mode on Chrome or upload it through the Chrome Web Store.

Essentially, once the browser is closed/refreshed and I run the game again, any information in the PlayerPrefs is gone. Also, a save file isn't created in the same place as a Web Player build does.