Not sure how important this is... but see bug 1155342. So what _can_ we flag a [NewObject] method with? We could use DependsOn=DeviceState if it's totally not dependent on the state of the DOM or anything, but I'd guess that's pretty rare: why would you return a new object each time if the contents of that object don't depend on anything at all about the DOM? We can't use DependsOn=DOMState, because that would allow LICM and CSE, which is clearly not OK for [NewObject] stuff. We can do DependsOn=Everything, but it turns out jitinfo has no useful thing it can do with DependsOn=Everything,Affects=Nothing because JitInfo::AliasSet has no useful value for that. Maybe we should fix _that_. Or maybe we should add a way to do DependsOn=(DeviceState,DOMState), since the former would just feed into movability while the latter feeds into the alias set. Or something. Opinions welcome.

Oh, once we do this, we may want to change what annotations setlike/maplike is using. Right now it's doing [DependsOn=Everything,Affects=Nothing] for some of its stuff.