Bug 662242: Swap out the old nsIURL IID for the new one, in nsBinaryInputStream::ReadObject. r=bz

xpcom/io/nsBinaryStream.cpp

@@ -60,6 +60,7 @@
 #include "nsISerializable.h"
 #include "nsIClassInfo.h"
 #include "nsComponentManagerUtils.h"
+#include "nsIURI.h" // for NS_IURI_IID
 
 NS_IMPL_ISUPPORTS3(nsBinaryOutputStream, nsIObjectOutputStream, nsIBinaryOutputStream, nsIOutputStream)
 
@@ -759,6 +760,20 @@ nsBinaryInputStream::ReadObject(PRBool aIsStrongRef, nsISupports* *aObject)
     rv = ReadID(&iid);
     NS_ENSURE_SUCCESS(rv, rv);
 
+    // HACK: Intercept old (pre-gecko6) nsIURI IID, and replace with
+    // the updated IID, so that we're QI'ing to an actual interface.
+    // (As soon as we drop support for upgrading from pre-gecko6, we can
+    // remove this chunk.)
+    static const nsIID oldURIiid =
+        { 0x7a22cc0, 0xce5, 0x11d3,
+          { 0x93, 0x31, 0x0, 0x10, 0x4b, 0xa0, 0xfd, 0x40 }};
+
+    if (iid.Equals(oldURIiid)) {
+        const nsIID newURIiid = NS_IURI_IID;
+        iid = newURIiid;
+    }
+    // END HACK
+
     nsCOMPtr<nsISupports> object = do_CreateInstance(cid, &rv);
     NS_ENSURE_SUCCESS(rv, rv);