Bug 112490 Patch to fix the mess I made
I have done bad things. I now prostrate myself and humbly ask that some gracious soul submit this patch (which I will attach forthwith) so that I may redeem myself. Basically, I (well really John but I made him do it) moved the ResourceMapping stuff to API but we missed a few things that needed to be done, causing great grief to the JDT team. Please spare the lashes as I have a low pain threshold.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/IContributorResourceAdapter2.java
/**
     * Return the resource mapping that the supplied adaptable 
     * adapts to. An <code>IContributorResourceAdapter2</code> assumes
     * that any object passed to it adapts to one equivalent
     * resource mapping.
     * 
     * @param adaptable the adaptable being queried
     * @return a resource mapping, or <code>null</code> if there
     *  is no adapted resource mapping for this type
     */
    public ResourceMapping getAdaptedResourceMapping(IAdaptable adaptable);
}