diff --git a/dom/src/jsurl/nsJSProtocolHandler.cpp b/dom/src/jsurl/nsJSProtocolHandler.cpp
index 8f9780f97853..c9775734cf45 100644
--- a/dom/src/jsurl/nsJSProtocolHandler.cpp
+++ b/dom/src/jsurl/nsJSProtocolHandler.cpp
@@ -335,7 +335,7 @@ nsresult nsJSThunk::BringUpConsole()
 // nsIStreamIO implementation...
 //
 NS_IMETHODIMP
-nsJSThunk::Open(char* *contentType, PRInt32 *contentLength)
+nsJSThunk::Open(PRInt32 *contentLength)
 {
     //
     // At this point the script has already been evaluated...
@@ -343,12 +343,23 @@ nsJSThunk::Open(char* *contentType, PRInt32 *contentLength)
     //
     // If the resultant script evaluation actually does return a value, we
     // treat it as html.
-    *contentType = nsCRT::strdup("text/html");
     *contentLength = mLength;
 
     return NS_OK;
 }
 
+
+NS_IMETHODIMP 
+nsJSThunk::GetContentType(char * *aContentType)
+{
+    *aContentType = nsCRT::strdup("text/html");
+    
+    if (*aContentType == nsnull)
+        return  NS_ERROR_OUT_OF_MEMORY;
+
+    return NS_OK;
+}
+
 NS_IMETHODIMP
 nsJSThunk::Close(nsresult status)
 {
diff --git a/modules/libjar/nsJARChannel.cpp b/modules/libjar/nsJARChannel.cpp
index e4b13d2b004a..73b5f721d3b1 100644
--- a/modules/libjar/nsJARChannel.cpp
+++ b/modules/libjar/nsJARChannel.cpp
@@ -240,7 +240,8 @@ nsJARChannel::OpenJARElement()
 {
     nsresult rv;
     nsAutoCMonitor mon(this);
-    rv = Open(nsnull, nsnull);
+    PRInt32 len;
+    rv = Open(&len); // is there a better way....  where is my C++ book?!
     if (NS_SUCCEEDED(rv))
         rv = GetInputStream(getter_AddRefs(mSynchronousInputStream));
     mon.Notify();       // wake up nsIChannel::Open
@@ -646,7 +647,7 @@ nsJARChannel::EnsureZipReader()
 }
 
 NS_IMETHODIMP
-nsJARChannel::Open(char* *contentType, PRInt32 *contentLength) 
+nsJARChannel::Open(PRInt32 *contentLength) 
 {
     nsresult rv;
     rv = EnsureZipReader();
@@ -661,10 +662,6 @@ nsJARChannel::Open(char* *contentType, PRInt32 *contentLength)
         if (NS_FAILED(rv)) return rv;
     }
 
-    if (contentType) {
-        rv = GetContentType(contentType);
-        if (NS_FAILED(rv)) return rv;
-    }
     return rv;
 }
 
diff --git a/modules/libjar/nsJARChannel.h b/modules/libjar/nsJARChannel.h
index 654a195d0c7f..0f1f7bb91479 100644
--- a/modules/libjar/nsJARChannel.h
+++ b/modules/libjar/nsJARChannel.h
@@ -84,9 +84,16 @@ public:
     NS_DECL_NSIJARCHANNEL
     NS_DECL_NSIREQUESTOBSERVER
     NS_DECL_NSISTREAMLISTENER
-    NS_DECL_NSISTREAMIO
     NS_DECL_NSIDOWNLOADOBSERVER
 
+    // NS_DECL_NSISTREAMIO and nsIChannel both define (attribute string contentType)
+
+    NS_IMETHOD Open(PRInt32 *contentLength);
+    NS_IMETHOD Close(nsresult status); 
+    NS_IMETHOD GetInputStream(nsIInputStream * *aInputStream);
+    NS_IMETHOD GetOutputStream(nsIOutputStream * *aOutputStream); 
+    NS_IMETHOD GetName(char * *aName); 
+
     nsJARChannel();
     virtual ~nsJARChannel();
 
diff --git a/netwerk/base/public/nsIStreamIO.idl b/netwerk/base/public/nsIStreamIO.idl
index a4e45df57b3f..1e6a9511e888 100644
--- a/netwerk/base/public/nsIStreamIO.idl
+++ b/netwerk/base/public/nsIStreamIO.idl
@@ -51,11 +51,10 @@ interface nsIFile;
 interface nsIStreamIO : nsISupports
 {
     /**
-     * Logically opens a stream I/O object, returning its content type
-     * and length. If either of these are unknown, the value -1 is returned.
+     * Logically opens a stream I/O object, returning its content length
+     * If this is unknown, the value -1 is returned.
      */
-    void open(out string contentType,
-              out long contentLength);
+    void open(out long contentLength);
 
     /**
      * Logically closes a stream I/O object. A status value is passed in
@@ -74,10 +73,15 @@ interface nsIStreamIO : nsISupports
     readonly attribute nsIOutputStream outputStream;
 
     /**
-     * Returns the 'name' of a stream I/O object. This name is often
+     * The 'name' of a stream I/O object. This name is often
      * used for display purposes.
      */
     readonly attribute string name;
+
+    /**
+     * Associated content type, if any.
+     **/
+    readonly attribute string contentType; 
 };
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/netwerk/base/src/nsFileStreams.cpp b/netwerk/base/src/nsFileStreams.cpp
index 508e2bb9da6d..98469cef8343 100644
--- a/netwerk/base/src/nsFileStreams.cpp
+++ b/netwerk/base/src/nsFileStreams.cpp
@@ -169,7 +169,7 @@ nsFileIO::GetFile(nsIFile* *aFile)
 }
 
 NS_IMETHODIMP
-nsFileIO::Open(char **contentType, PRInt32 *contentLength)
+nsFileIO::Open(PRInt32 *contentLength)
 {
     NS_ASSERTION(mFile, "File must not be null");
     if (mFile == nsnull)
@@ -177,9 +177,7 @@ nsFileIO::Open(char **contentType, PRInt32 *contentLength)
 
     if (contentLength)
         *contentLength = 0;
-    if (contentType)
-        *contentType = nsnull;
-
+ 
     nsresult rv = NS_OK;
     nsCOMPtr<nsILocalFile> localFile = do_QueryInterface(mFile, &rv);
     if (NS_FAILED(rv)) return rv;
@@ -193,13 +191,6 @@ nsFileIO::Open(char **contentType, PRInt32 *contentLength)
         PRBool isDir;
         rv = localFile->IsDirectory(&isDir);
         if (NS_SUCCEEDED(rv) && isDir) {
-            // Directories turn into an HTTP-index stream, with
-            // unbounded (i.e., read 'til the stream says it's done)
-            // length.
-            if (contentType)
-                *contentType = nsCRT::strdup(APPLICATION_HTTP_INDEX_FORMAT);
-            if (contentLength) 
-                *contentLength = -1;
             return NS_OK;
         }
         return NS_ERROR_FILE_NOT_FOUND;
@@ -219,30 +210,45 @@ nsFileIO::Open(char **contentType, PRInt32 *contentLength)
         else 
             *contentLength = -1;
     }
-    if (contentType) {
-        // must we really go though this? dougt
-        nsIMIMEService* mimeServ = nsnull;
-        nsFileTransportService* fileTransportService = nsFileTransportService::GetInstance();
-        if (fileTransportService) {
-            mimeServ = fileTransportService->GetCachedMimeService();
-            if (mimeServ)
-                rv = mimeServ->GetTypeFromFile(mFile, contentType);
-        }
-        
-        if (!mimeServ || (NS_FAILED(rv))) {
-            // if all else fails treat it as text/html?
-            *contentType = nsCRT::strdup(UNKNOWN_CONTENT_TYPE);
-            if (*contentType == nsnull)
-                rv = NS_ERROR_OUT_OF_MEMORY;
-            else
-                rv = NS_OK;
-        }
-    }
     PR_LOG(gFileIOLog, PR_LOG_DEBUG,
            ("nsFileIO: logically opening %s", mSpec));
     return rv;
 }
 
+
+NS_IMETHODIMP 
+nsFileIO::GetContentType(char * *aContentType)
+{
+    if (!mContentType.IsEmpty()) {
+        *aContentType = ToNewCString(mContentType);
+        return NS_OK;
+    }
+
+    if (mFile == nsnull)
+        return NS_ERROR_NOT_INITIALIZED;
+
+    nsresult rv = NS_OK;
+    nsIMIMEService* mimeServ = nsnull;
+    nsFileTransportService* fileTransportService = nsFileTransportService::GetInstance();
+    if (fileTransportService) {
+        mimeServ = fileTransportService->GetCachedMimeService();
+        if (mimeServ)
+            rv = mimeServ->GetTypeFromFile(mFile, aContentType);
+    }
+        
+    if (!mimeServ || (NS_FAILED(rv))) {
+        // if all else fails treat it as text/html?
+        *aContentType = nsCRT::strdup(UNKNOWN_CONTENT_TYPE);
+        if (*aContentType == nsnull)
+            rv = NS_ERROR_OUT_OF_MEMORY;
+        else
+            rv = NS_OK;
+    }
+
+    mContentType.Assign(*aContentType);
+    return rv;
+}
+
 NS_IMETHODIMP
 nsFileIO::Close(nsresult status)
 {
@@ -266,7 +272,7 @@ nsFileIO::GetInputStream(nsIInputStream * *aInputStream)
     nsresult rv;
 
     if (!mFD) {
-        rv = Open(nsnull, nsnull);        
+        rv = Open(nsnull);        
         if (NS_FAILED(rv))  // file or directory does not exist
             return rv;
     }
@@ -319,7 +325,7 @@ nsFileIO::GetOutputStream(nsIOutputStream * *aOutputStream)
     nsresult rv;
 
     if (!mFD) {
-        rv = Open(nsnull, nsnull);
+        rv = Open(nsnull);
         if (NS_FAILED(rv))  // file or directory does not exist
             return rv;
     }
diff --git a/netwerk/base/src/nsFileStreams.h b/netwerk/base/src/nsFileStreams.h
index 34be56661770..f7b129a901eb 100644
--- a/netwerk/base/src/nsFileStreams.h
+++ b/netwerk/base/src/nsFileStreams.h
@@ -70,6 +70,7 @@ protected:
     PRInt32             mIOFlags;
     PRInt32             mPerm;
     nsresult            mStatus;
+    nsCString           mContentType;
 #ifdef PR_LOGGING
     char*               mSpec;
 #endif
diff --git a/netwerk/base/src/nsFileTransport.cpp b/netwerk/base/src/nsFileTransport.cpp
index c305e6f14160..0d6e5a8a819f 100644
--- a/netwerk/base/src/nsFileTransport.cpp
+++ b/netwerk/base/src/nsFileTransport.cpp
@@ -208,8 +208,7 @@ NS_IMPL_THREADSAFE_ISUPPORTS1(nsFileTransportSinkWrapper, nsIOutputStream)
 //////////////////////////////////////////////////////////////////////////////////
 
 nsFileTransport::nsFileTransport()
-    : mContentType(nsnull),
-      mBufferSegmentSize(NS_FILE_TRANSPORT_DEFAULT_SEGMENT_SIZE),
+    : mBufferSegmentSize(NS_FILE_TRANSPORT_DEFAULT_SEGMENT_SIZE),
       mBufferMaxSize(NS_FILE_TRANSPORT_DEFAULT_BUFFER_SIZE),
       mXferState(CLOSED),
       mRunState(RUNNING),
@@ -292,11 +291,6 @@ nsFileTransport::~nsFileTransport()
         PR_DestroyLock(mLock);
         mLock = nsnull;
     }
-    if (mContentType) {
-        nsCRT::free(mContentType);
-        mContentType = nsnull;
-    }
-
     NS_IF_RELEASE(mService);
 }
 
@@ -652,7 +646,7 @@ nsFileTransport::Process(nsIProgressEventSink *progressSink)
 
     switch (mXferState) {
       case OPEN_FOR_READ: { 
-        mStatus = mStreamIO->Open(&mContentType, &mTotalAmount);
+        mStatus = mStreamIO->Open(&mTotalAmount);
         LOG(("nsFileTransport: OPEN_FOR_READ [this=%x %s] status=%x\n", this, mStreamName.get(), mStatus));
         if (mListener) {
             nsresult rv = mListener->OnStartRequest(this, mContext);  // always send the start notification
@@ -842,7 +836,7 @@ nsFileTransport::Process(nsIProgressEventSink *progressSink)
       case OPEN_FOR_WRITE: {
         LOG(("nsFileTransport: OPEN_FOR_WRITE [this=%x %s]\n",
             this, mStreamName.get()));
-        mStatus = mStreamIO->Open(&mContentType, &mTotalAmount);
+        mStatus = mStreamIO->Open(&mTotalAmount);
         
         if (mStatus == NS_ERROR_FILE_NOT_FOUND)
             mStatus = NS_OK;
diff --git a/netwerk/base/src/nsFileTransport.h b/netwerk/base/src/nsFileTransport.h
index 97edf81ccf1c..231806ea770b 100644
--- a/netwerk/base/src/nsFileTransport.h
+++ b/netwerk/base/src/nsFileTransport.h
@@ -122,7 +122,6 @@ protected:
     nsCOMPtr<nsIProgressEventSink>      mProgressSink;
     nsCOMPtr<nsIInterfaceRequestor>     mNotificationCallbacks;
     nsCOMPtr<nsIStreamIO>               mStreamIO;
-    char                               *mContentType;
     PRUint32                            mBufferSegmentSize;
     PRUint32                            mBufferMaxSize;
 
diff --git a/netwerk/base/src/nsInputStreamChannel.cpp b/netwerk/base/src/nsInputStreamChannel.cpp
index 7afcb5af5afd..7e8ebe9b7d48 100644
--- a/netwerk/base/src/nsInputStreamChannel.cpp
+++ b/netwerk/base/src/nsInputStreamChannel.cpp
@@ -106,23 +106,34 @@ nsInputStreamIO::Init(const char* name, nsIInputStream* input,
 }
 
 NS_IMETHODIMP
-nsInputStreamIO::Open(char **contentType, PRInt32 *contentLength)
+nsInputStreamIO::Open(PRInt32 *contentLength)
 {
-    *contentType = nsCRT::strdup(mContentType);
-    if (*contentType == nsnull)
-        return NS_ERROR_OUT_OF_MEMORY;
     *contentLength = mContentLength;
     return NS_OK;
 }
 
+
+NS_IMETHODIMP 
+nsInputStreamIO::GetContentType(char * *aContentType)
+{
+    if (!mContentType) {
+        return NS_ERROR_OUT_OF_MEMORY;
+    }
+    *aContentType = nsCRT::strdup(mContentType);
+    if (*aContentType == nsnull)
+        return NS_ERROR_OUT_OF_MEMORY;
+
+    return NS_OK;
+}
+
 NS_IMETHODIMP
 nsInputStreamIO::Close(nsresult status)
 {
     mStatus = status;
     if (mInputStream)
         return mInputStream->Close();
-    else
-        return NS_OK;
+
+    return NS_OK;
 }
 
 NS_IMETHODIMP
@@ -152,7 +163,7 @@ nsInputStreamIO::GetName(char* *aName)
 // nsStreamIOChannel methods:
 
 nsStreamIOChannel::nsStreamIOChannel()
-    : mContentType(nsnull), mContentLength(-1),
+    : mOpened(PR_FALSE), mContentType(nsnull), mContentLength(-1),
       mBufferSegmentSize(0), mBufferMaxSize(0),
       mLoadFlags(LOAD_NORMAL), mStatus(NS_OK)
 {
@@ -291,7 +302,10 @@ nsStreamIOChannel::GetURI(nsIURI* *aURI)
 NS_IMETHODIMP
 nsStreamIOChannel::Open(nsIInputStream **result)
 {
-    return mStreamIO->GetInputStream(result);
+    nsresult rv = mStreamIO->GetInputStream(result);
+    if (NS_SUCCEEDED(rv))
+        mOpened = PR_TRUE;
+    return rv;
 }
 
 NS_IMETHODIMP
@@ -314,6 +328,7 @@ nsStreamIOChannel::AsyncOpen(nsIStreamListener *listener, nsISupports *ctxt)
 
         rv = fts->CreateTransportFromStreamIO(mStreamIO, getter_AddRefs(mFileTransport));
         if (NS_FAILED(rv)) goto done;
+        mOpened = PR_TRUE;
     }
 
     // Hook up the notification callbacks InterfaceRequestor...
@@ -325,12 +340,6 @@ nsStreamIOChannel::AsyncOpen(nsIStreamListener *listener, nsISupports *ctxt)
         if (NS_FAILED(rv)) goto done;
     }
 
-#if 0
-    if (mContentType == nsnull) {
-        rv = mStreamIO->Open(&mContentType, &mContentLength);
-        if (NS_FAILED(rv)) goto done;
-    }
-#endif
     rv = mFileTransport->AsyncRead(this, ctxt, 0, PRUint32(-1), 0, getter_AddRefs(mRequest));
 
   done:
@@ -417,7 +426,12 @@ nsStreamIOChannel::GetContentType(char * *aContentType)
 {
     nsresult rv;
     if (mContentType == nsnull) {
-        rv = mStreamIO->Open(&mContentType, &mContentLength);
+        if (!mOpened) {
+            rv = mStreamIO->Open(&mContentLength);
+            if (NS_FAILED(rv)) return rv;
+            mOpened = PR_TRUE;
+        }
+        mStreamIO->GetContentType(&mContentType);
         if (NS_FAILED(rv)) return rv;
     }
     *aContentType = nsCRT::strdup(mContentType);
@@ -441,9 +455,10 @@ NS_IMETHODIMP
 nsStreamIOChannel::GetContentLength(PRInt32 *aContentLength)
 {
     nsresult rv;
-    if (mContentType == nsnull) {
-        rv = mStreamIO->Open(&mContentType, &mContentLength);
+    if (!mOpened) {
+        rv = mStreamIO->Open(&mContentLength);
         if (NS_FAILED(rv)) return rv;
+        mOpened = PR_TRUE;
     }
     *aContentLength = mContentLength;
     return NS_OK;
@@ -483,6 +498,7 @@ nsStreamIOChannel::OnStopRequest(nsIRequest *request, nsISupports* context, nsre
 
     // Make sure the stream io is closed
     mStreamIO->Close(aStatus);
+    mOpened = PR_FALSE;
 
     // There is no point in returning anything other than NS_OK
     return NS_OK;
diff --git a/netwerk/base/src/nsInputStreamChannel.h b/netwerk/base/src/nsInputStreamChannel.h
index 1b970d838a07..258b4a7bea0d 100644
--- a/netwerk/base/src/nsInputStreamChannel.h
+++ b/netwerk/base/src/nsInputStreamChannel.h
@@ -108,6 +108,7 @@ protected:
     nsCOMPtr<nsIProgressEventSink>      mProgressSink;
     nsCOMPtr<nsIURI>                    mOriginalURI;
     nsCOMPtr<nsIURI>                    mURI;
+    PRBool                              mOpened;
     char*                               mContentType;
     PRInt32                             mContentLength;
     nsCOMPtr<nsIStreamIO>               mStreamIO;
diff --git a/netwerk/protocol/jar/src/nsJARChannel.cpp b/netwerk/protocol/jar/src/nsJARChannel.cpp
index e4b13d2b004a..73b5f721d3b1 100644
--- a/netwerk/protocol/jar/src/nsJARChannel.cpp
+++ b/netwerk/protocol/jar/src/nsJARChannel.cpp
@@ -240,7 +240,8 @@ nsJARChannel::OpenJARElement()
 {
     nsresult rv;
     nsAutoCMonitor mon(this);
-    rv = Open(nsnull, nsnull);
+    PRInt32 len;
+    rv = Open(&len); // is there a better way....  where is my C++ book?!
     if (NS_SUCCEEDED(rv))
         rv = GetInputStream(getter_AddRefs(mSynchronousInputStream));
     mon.Notify();       // wake up nsIChannel::Open
@@ -646,7 +647,7 @@ nsJARChannel::EnsureZipReader()
 }
 
 NS_IMETHODIMP
-nsJARChannel::Open(char* *contentType, PRInt32 *contentLength) 
+nsJARChannel::Open(PRInt32 *contentLength) 
 {
     nsresult rv;
     rv = EnsureZipReader();
@@ -661,10 +662,6 @@ nsJARChannel::Open(char* *contentType, PRInt32 *contentLength)
         if (NS_FAILED(rv)) return rv;
     }
 
-    if (contentType) {
-        rv = GetContentType(contentType);
-        if (NS_FAILED(rv)) return rv;
-    }
     return rv;
 }
 
diff --git a/netwerk/protocol/jar/src/nsJARChannel.h b/netwerk/protocol/jar/src/nsJARChannel.h
index 654a195d0c7f..0f1f7bb91479 100644
--- a/netwerk/protocol/jar/src/nsJARChannel.h
+++ b/netwerk/protocol/jar/src/nsJARChannel.h
@@ -84,9 +84,16 @@ public:
     NS_DECL_NSIJARCHANNEL
     NS_DECL_NSIREQUESTOBSERVER
     NS_DECL_NSISTREAMLISTENER
-    NS_DECL_NSISTREAMIO
     NS_DECL_NSIDOWNLOADOBSERVER
 
+    // NS_DECL_NSISTREAMIO and nsIChannel both define (attribute string contentType)
+
+    NS_IMETHOD Open(PRInt32 *contentLength);
+    NS_IMETHOD Close(nsresult status); 
+    NS_IMETHOD GetInputStream(nsIInputStream * *aInputStream);
+    NS_IMETHOD GetOutputStream(nsIOutputStream * *aOutputStream); 
+    NS_IMETHOD GetName(char * *aName); 
+
     nsJARChannel();
     virtual ~nsJARChannel();