The file channel needs to implement nsIProgressEventSink, so the channel parameter is *not* the file transport. Doing this means that the FileChannel also needs to implement nsIInterfaceRequestor...

netwerk/protocol/file/src/nsFileChannel.cpp

@@ -83,12 +83,14 @@ nsFileChannel::~nsFileChannel()
 {
 }
 
-NS_IMPL_THREADSAFE_ISUPPORTS5(nsFileChannel,
+NS_IMPL_THREADSAFE_ISUPPORTS7(nsFileChannel,
                    nsIFileChannel,
                    nsIChannel,
                    nsIRequest,
                    nsIStreamListener,
-                   nsIStreamObserver)
+                   nsIStreamObserver,
+                   nsIProgressEventSink,
+                   nsIInterfaceRequestor)
 
 NS_METHOD
 nsFileChannel::Create(nsISupports* aOuter, const nsIID& aIID, void* *aResult)
@@ -222,7 +224,7 @@ nsFileChannel::EnsureTransport()
         if (NS_FAILED(rv)) return rv;
     }
     if (mCallbacks) {
-        rv = mFileTransport->SetNotificationCallbacks(mCallbacks);
+        rv = mFileTransport->SetNotificationCallbacks(this);
         if (NS_FAILED(rv)) return rv;
     }
     if (mTransferOffset) {
@@ -586,6 +588,13 @@ NS_IMETHODIMP
 nsFileChannel::SetNotificationCallbacks(nsIInterfaceRequestor* aNotificationCallbacks)
 {
   mCallbacks = aNotificationCallbacks;
+
+  // Cache the new nsIProgressEventSink instance...
+  if (mCallbacks) {
+    (void)mCallbacks->GetInterface(NS_GET_IID(nsIProgressEventSink),
+                                   getter_AddRefs(mProgress));
+  }
+
   return NS_OK;
 }
 
@@ -661,6 +670,57 @@ nsFileChannel::OnDataAvailable(nsIChannel* transportChannel, nsISupports* contex
     return rv;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// From nsIInterfaceRequestor
+////////////////////////////////////////////////////////////////////////////////
+
+NS_IMETHODIMP
+nsFileChannel::GetInterface(const nsIID &anIID, void **aResult )
+{
+    // capture the progress event sink stuff. pass the rest through.
+    if (anIID.Equals(NS_GET_IID(nsIProgressEventSink))) {
+        *aResult = NS_STATIC_CAST(nsIProgressEventSink*, this);
+        NS_ADDREF(this);
+        return NS_OK;
+    } 
+    else if (mCallbacks) {
+        return mCallbacks->GetInterface(anIID, aResult);
+    }
+    return NS_ERROR_NO_INTERFACE;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// From nsIProgressEventSink
+////////////////////////////////////////////////////////////////////////////////
+
+NS_IMETHODIMP
+nsFileChannel::OnStatus(nsIChannel *aChannel,
+                        nsISupports *aContext,
+                        const PRUnichar *aMsg)
+{
+    nsresult rv = NS_OK;
+
+    if (mProgress) {
+        mProgress->OnStatus(this, aContext, aMsg);
+    }
+    return rv;
+}
+
+NS_IMETHODIMP
+nsFileChannel::OnProgress(nsIChannel* aChannel,
+                          nsISupports* aContext,
+                          PRUint32 aProgress,
+                          PRUint32 aProgressMax)
+{
+    nsresult rv = NS_OK;
+
+    if (mProgress) {
+        rv = mProgress->OnProgress(this, aContext, aProgress, aProgressMax);
+    }
+    return rv;
+}
+
+
 ////////////////////////////////////////////////////////////////////////////////
 // From nsIFileChannel
 ////////////////////////////////////////////////////////////////////////////////

netwerk/protocol/file/src/nsFileChannel.h

@@ -27,7 +27,6 @@
 #include "nsIInterfaceRequestor.h"
 #include "nsILoadGroup.h"
 #include "nsIStreamListener.h"
-#include "nsIChannel.h"
 #include "nsFileSpec.h"
 #include "nsIURI.h"
 #include "nsCOMPtr.h"
@@ -36,21 +35,24 @@
 #include "prlock.h"
 #include "nsIEventQueueService.h"
 #include "nsIPipe.h"
-#include "nsILoadGroup.h"
-#include "nsIStreamListener.h"
 #include "nsCOMPtr.h"
 #include "nsIFile.h"        /* Solaris/gcc needed this here. */
+#include "nsIProgressEventSink.h"
 
 class nsFileChannel : public nsIFileChannel,
-                      public nsIStreamListener
+                      public nsIInterfaceRequestor,
+                      public nsIStreamListener,
+                      public nsIProgressEventSink
 {
 public:
     NS_DECL_ISUPPORTS
     NS_DECL_NSIREQUEST
     NS_DECL_NSICHANNEL
     NS_DECL_NSIFILECHANNEL
+    NS_DECL_NSIINTERFACEREQUESTOR
     NS_DECL_NSISTREAMOBSERVER
     NS_DECL_NSISTREAMLISTENER
+    NS_DECL_NSIPROGRESSEVENTSINK
 
     nsFileChannel();
     // Always make the destructor virtual: 
@@ -81,6 +83,7 @@ protected:
     PRUint32                            mBufferSegmentSize;
     PRUint32                            mBufferMaxSize;
     nsresult                            mStatus;
+    nsCOMPtr<nsIProgressEventSink>      mProgress;
 #ifdef DEBUG
     PRThread*                           mInitiator;
 #endif