Bug 702256 added a new brightness API, which makes nsIScreen_MOZILLA_2_0_BRANCH redundant. The interface only appears to be used once in the tree (http://mxr.mozilla.org/mozilla-central/source/mobile/xul/chrome/content/common-ui.js#1179) to ensure that the screen stays on whilst watching videos fullscreen. Presume we want to convert that instance to the new API and then depreciate and/or remove nsIScreen_MOZILLA_2_0_BRANCH (not sure what the addons situation is). Once that is done, bug 672166 will be redundant. http://mxr.mozilla.org/mozilla-central/search?string=nsIScreen_MOZILLA_2_0_BRANCH

Now that I've thought about this more, maybe these should stay as separate APIs. The mozBrightness API is for devices where we control the screen's brightness. There's no auto-shutoff to speak of. But on devices where the screen automatically dims or shuts off, mozBrightness doesn't make much sense, and this API is more suitable.

True; happy to wontfix if you like?

Yes, I think so. There's some work around power APIs right now, so we may yet get rid of this one.