In the previous patch, one of the files which was deleted is ShimInterfaceInfo.
This is an implementor of nsIInterfaceInfo which exists for legacy reasons, in
order to allow Components.interfaces.nsIDOM* to have the correct constants and
IIDs associated with them.
As that file was deleted, this information now has to be stored in the typelib.
To do this, the information is moved to the xptshim and xptshimfile attributes
on the relevant xpcom interfaces.
xptshim(...) means that this xpcom interface is a shim for the WebIDL interface
with the specified name.
xptshimfile(...) is for use when the webidl interface is declared in another
interface's .webidl file, (in our case, MessageManager.webidl). It contains the
name of the parent binding, such that we can #include the correct file in our
generated code.
This patch does not add the code which uses these changes, only the parsing
logic.
