A request observer proxy is used to ship data over to another thread
 specified by the thread's dispatch target. The "true" request observer's
 methods are invoked on the other thread.

 This interface only provides the initialization needed after construction.
 Otherwise, these objects are used simply as nsIRequestObserver's.
[scriptable, uuid(7df8845f-938a-4437-9ea4-b11b850048f1)]
interface nsIRequestObserverProxy : nsIRequestObserver

Methods

 Initializes an nsIRequestObserverProxy.

 @param observer - receives observer notifications on the other thread
 @param target - may be NULL indicating the calling thread's event target
void init(in nsIRequestObserver observer, in nsIEventTarget target)