Fix list output stream

runtime/bin/list_stream.dart

Index: runtime/bin/list_stream.dart
diff --git a/runtime/bin/list_stream.dart b/runtime/bin/list_stream.dart
index 79e8a7dd3f84ab85597771c2d17032e3a6371f07..da5826ec8e956bbec2039d07d62e81b6fb8fc7ad 100644
--- a/runtime/bin/list_stream.dart
+++ b/runtime/bin/list_stream.dart
@@ -71,12 +71,14 @@ class ListOutputStream implements OutputStream {
     } else {
       _bufferList.add(buffer);
     }
+    return true;
   }
 
   bool writeFrom(List<int> buffer, [int offset = 0, int len]) {
     if (_streamMarkedClosed) throw new StreamException.streamClosed();
     _bufferList.add(
         buffer.getRange(offset, (len == null) ? buffer.length - offset : len));
+    return true;
   }
 
   void close() {