Turns out that there aren't nearly as many dead interfaces (derived from nsISupports) in Moz as one would expect. 7/10 unimplemented ones are public interfaces. Note that I'm also processing testcases, so there aren't any testcases for these.
Here is the script I used to find them. http://hg.mozilla.org/oink/?file/0ab46e97549e/dehydra_scripts/find_single_impl.js
Here are my stats:
6375 classes derived from nsISupports
layout/style/nsCSSAnonBoxes.h:48: nsICSSAnonBoxPseudo has no class members.
layout/style/nsCSSPseudoElements.h:48: nsICSSPseudoElement has no class members.
layout/style/nsCSSPseudoClasses.h:48: nsICSSPseudoClass has no class members.
355 valid non-XPIDL interfaces
Only one implementation: 153
No Implementation: 10
I wonder if nsIDOMSVGListener and nsIDOMSVGZoomListener are used by svg zoom/pan extensions e.g. bug 163068 comment 32
I suggested we use sort -u | comm -23 to set-difference the list taras produced minus the mozpad list of known-useful platform interfaces, to get a hit-list. Thoughts?
nsIXFormsUtilityService is used at least by xforms extension.
nsWebNavigationBaseCommand is not an interface.
(In reply to comment #3)
> nsIXFormsUtilityService is used at least by xforms extension.
as well by accessibility.
The SVG interfaces were removed in bug 499665. If there are any other unused interfaces then I guess they need a new bug with a different component.