Bug 723498. Make sure to always set our out param in nsMultiplexInputStream::IsNonBlocking when returning success. r=bsmedberg

xpcom/io/nsMultiplexInputStream.cpp

@@ -331,6 +331,14 @@ NS_IMETHODIMP
 nsMultiplexInputStream::IsNonBlocking(bool *aNonBlocking)
 {
     PRUint32 len = mStreams.Count();
+    if (len == 0) {
+        // Claim to be non-blocking, since we won't block the caller.
+        // On the other hand we'll never return NS_BASE_STREAM_WOULD_BLOCK,
+        // so maybe we should claim to be blocking?  It probably doesn't
+        // matter in practice.
+        *aNonBlocking = true;
+        return NS_OK;
+    }
     for (PRUint32 i = 0; i < len; ++i) {
         nsresult rv = mStreams[i]->IsNonBlocking(aNonBlocking);
         NS_ENSURE_SUCCESS(rv, rv);