Prefs is a general-purpose key-value store for application preferences.

At the moment, src/base/prefs has a bunch of dependencies back to
src/chrome, and thus should only be used by code under src/chrome.

We are working to remove these dependencies; once we do so,
src/base/prefs will be available as a separate module, 'base_prefs',
from src/base/base.gyp.

Until that happens, please do not try to reuse outside of chrome/.
