diff --git a/talk/app/webrtc/datachannelinterface.h b/talk/app/webrtc/datachannelinterface.h
index 6054e1b..82d375c 100644
--- a/talk/app/webrtc/datachannelinterface.h
+++ b/talk/app/webrtc/datachannelinterface.h
@@ -75,6 +75,8 @@
       : data(text.data(), text.length()),
         binary(false) {
   }
+  size_t size() const { return data.length(); }
+
   talk_base::Buffer data;
   // Indicates if the received data contains UTF-8 or binary data.
   // Note that the upper layers are left to verify the UTF-8 encoding.