Usage of imgIRequest Interface

 Start the load and decode of an image.
 @param aURI the URI to load
 @param aInitialDocumentURI the URI that 'initiated' the load -- used for 3rd party cookie blocking
 @param aReferrerURI the 'referring' URI
 @param aLoadGroup Loadgroup to put the image load into
 @param aObserver the observer
 @param aCX some random data
 @param aLoadFlags Load flags for the request
 @param aCacheKey cache key to use for a load if the original
                  image came from a request that had post data
 @param aRequest A newly created, unused imgIRequest object or NULL for one to
                     be created for you.


 libpr0n does NOT keep a strong ref to the observer; this prevents
 reference cycles.  This means that callers of loadImage should
 make sure to Cancel() the resulting request before the observer
 goes away.

[noscript] imgIRequest loadImage(in nsIURI aURI, in nsIURI aInitialDocumentURL, in nsIURI aReferrerURI, in nsILoadGroup aLoadGroup, in imgIDecoderObserver aObserver, in nsISupports aCX, in nsLoadFlags aLoadFlags, in nsISupports cacheKey, in imgIRequest aRequest)

 Start the load and decode of an image.
 @param aChannel the channel to load the image from.  This must
                 already be opened before ths method is called, and there
                 must have been no OnDataAvailable calls for it yet.   
 @param aObserver the observer
 @param cx some random data
 @param aListener [out]
        A listener that should receive the data. Can be null, in which
        case imagelib has found a cached image and is not interested in
        the data. The caller needs not cancel the channel in this case.

 libpr0n does NOT keep a strong ref to the observer; this prevents
 reference cycles.  This means that callers of loadImageWithChannel should
 make sure to Cancel() the resulting request before the observer goes away.

[noscript] imgIRequest loadImageWithChannel(in nsIChannel aChannel, in imgIDecoderObserver aObserver, in nsISupports cx, out nsIStreamListener aListener)

 Clone this request; the returned request will have aObserver as the
 observer.  aObserver will be notified synchronously (before the clone()
 call returns) with all the notifications that have already been dispatched
 for this image load.

imgIRequest clone(in imgIDecoderObserver aObserver)

 Accessor to get the image requests

 @param aRequestType a value saying which request is wanted

 @return the imgIRequest object (may be null, even when no error
 is thrown)

 @throws NS_ERROR_UNEXPECTED if the request type requested is not
 known

imgIRequest getRequest(in long aRequestType)

 called when some part of the frame has new data in it

[noscript] void onDataAvailable(in imgIRequest aRequest, in gfxIImageFrame aFrame, [const] in nsIntRect aRect)

 called once the image has been inited and therefore has a width and height

void onStartContainer(in imgIRequest aRequest, in imgIContainer aContainer)

 called as soon as the image begins getting decoded

void onStartDecode(in imgIRequest aRequest)

 called when each frame is created

void onStartFrame(in imgIRequest aRequest, in gfxIImageFrame aFrame)

 called at the same time that nsIRequestObserver::onStartRequest would be
 (used only for observers of imgIRequest objects, which are nsIRequests,
 not imgIDecoder objects)

 Unlike nsIRequestObserver::onStartRequest, this can be called
 synchronously.

void onStartRequest(in imgIRequest aRequest)

 probably not needed.  called right before onStopDecode

void onStopContainer(in imgIRequest aRequest, in imgIContainer aContainer)

 called when the decoder is dying off

void onStopDecode(in imgIRequest aRequest, in nsresult status, in wstring statusArg)

 called when a frame is finished decoding

void onStopFrame(in imgIRequest aRequest, in gfxIImageFrame aFrame)

 called at the same time that nsIRequestObserver::onStopRequest would be
 (used only for observers of imgIRequest objects, which are nsIRequests,
 not imgIDecoder objects)

 Unlike nsIRequestObserver::onStartRequest, this can be called
 synchronously.

void onStopRequest(in imgIRequest aRequest, in boolean aIsLastPart)

 Start the load and decode of an image.
 @param aURI the URI to load
 @param aInitialDocumentURI the URI that 'initiated' the load -- used for 3rd party cookie blocking
 @param aReferrerURI the 'referring' URI
 @param aLoadGroup Loadgroup to put the image load into
 @param aObserver the observer
 @param aCX some random data
 @param aLoadFlags Load flags for the request
 @param aCacheKey cache key to use for a load if the original
                  image came from a request that had post data
 @param aRequest A newly created, unused imgIRequest object or NULL for one to
                     be created for you.


 libpr0n does NOT keep a strong ref to the observer; this prevents
 reference cycles.  This means that callers of loadImage should
 make sure to Cancel() the resulting request before the observer
 goes away.

[noscript] imgIRequest loadImage(in nsIURI aURI, in nsIURI aInitialDocumentURL, in nsIURI aReferrerURI, in nsILoadGroup aLoadGroup, in imgIDecoderObserver aObserver, in nsISupports aCX, in nsLoadFlags aLoadFlags, in nsISupports cacheKey, in imgIRequest aRequest)

 Used to find out what type of request one is dealing with (eg
 which request got passed through to the imgIDecoderObserver
 interface of an observer)

 @param aRequest the request whose type we want to know

 @return an enum value saying what type this request is

 @throws NS_ERROR_UNEXPECTED if aRequest is not known

long getRequestType(in imgIRequest aRequest)