As far as I can tell, the WebIDL specification doesn't define anything
about what really happens when a constructor is invoked, once the
arguments have been converted to the IDL types, except the conversion of
the return value from an IDL type to an ES type. It defers the exact
behavior of the constructor to the specification defining the constructor.
XHR2 currently says in http://www.w3.org/TR/XMLHttpRequest2/#constructors :
The XMLHttpRequest() constructor must return a new XMLHttpRequest
object.
and in http://www.w3.org/TR/XMLHttpRequest2/#origin-and-base-url :
In environments where the global object is represented by the Window
object the XMLHttpRequest object has an associated XMLHttpRequest
document which is the document associated with the Window object for
which the XMLHttpRequest interface object was created.
Now consider a web page with two subframes and a script that has
references to the two subframe windows in variables w1 and w2. Then the
script does this:
w1.XMLHttpRequest = w2.XMLHttpRequest;
var xhr = new w1.XMLHttpRequest();
What's the document associated with xhr? Is it w1.document,
w2.document, or window.document? The concept "the Window object for
which the XMLHttpRequest interface object was created" doesn't seem to
be defined anywhere....
-Boris
