HTTP2 draft 13: support unknown frame types and settings types as extensions.

net/spdy/spdy_framer.h

Index: net/spdy/spdy_framer.h
diff --git a/net/spdy/spdy_framer.h b/net/spdy/spdy_framer.h
index 85576f5099d6fdd161d65e619e3787e63a5e7c57..42711c2df841df63f459fc899a487e917024b9a6 100644
--- a/net/spdy/spdy_framer.h
+++ b/net/spdy/spdy_framer.h
@@ -289,7 +289,13 @@ class NET_EXPORT_PRIVATE SpdyFramerVisitorInterface {
   virtual void OnPriority(SpdyStreamId stream_id,
                           SpdyStreamId parent_stream_id,
                           uint8 weight,
-                          bool exclusive) {};
+                          bool exclusive) {}
+
+  // Called when a frame type we don't recognize is received.
+  // Return true if this appears to be a valid extension frame, false otherwise.
+  // We distinguish between extension frames and nonsense by checking
+  // whether the stream id is valid.
+  virtual bool OnUnknownFrame(SpdyStreamId stream_id, int frame_type) = 0;
 };
 
 // Optionally, and in addition to SpdyFramerVisitorInterface, a class supporting