Maplike

Hey,

I was exploring Maplike to use in the context of the Web MIDI
API<http://webaudio.github.io/web-midi-api/>(which contains a pair of
unordered, keyed collections of MIDI ports
available to the UA), and I had a few questions I wanted to raise/ask the
status of.

First comment - the missing bits defining iterators in
http://dev.w3.org/2006/webapi/WebIDL/#es-map-members is, of course, a
little problematic, because I'll have to make something up.  Tab mentioned
the ES spec has these defined; should I go there for the definitions?

The second item is an explicit ask I have: Maps seem explicitly oriented
toward read/write collections; aka, in order not to violate the definition
of Map members, I will have to declare clear(), delete() and set() (and
explicitly say they do nothing, as you shouldn't be able to "remove" MIDI
ports, or some wiseass is going to ask how to restore them).

My hope is that it's feasible to say that any readonly attribute whose
value is a MapClass interface is automatically readonly with respect to the
map itself, such that set/clear/delete all throw or silently fail or
something.

Thoughts?

-Chris