Add SpdyFramerDebugVisitorInterface for later usage in stats collecting

net/spdy/spdy_framer.cc

Index: net/spdy/spdy_framer.cc
diff --git a/net/spdy/spdy_framer.cc b/net/spdy/spdy_framer.cc
index 94ab6d1cf2f975a6a9f0cb0448e3a957154a1b82..d0610c2062dd3394c23bbd9cc7f91624c74e1aec 100644
--- a/net/spdy/spdy_framer.cc
+++ b/net/spdy/spdy_framer.cc
@@ -123,6 +123,7 @@ SpdyFramer::SpdyFramer(int version)
       current_frame_len_(0),
       enable_compression_(true),
       visitor_(NULL),
+      debug_visitor_(NULL),
       display_protocol_("SPDY"),
       spdy_version_(version),
       syn_frame_processed_(false),
@@ -1676,6 +1677,10 @@ SpdyControlFrame* SpdyFramer::CompressControlFrame(
   if (visitor_)
     visitor_->OnControlFrameCompressed(frame, *new_frame);
 
+  if (debug_visitor_ != NULL) {
+    debug_visitor_->OnCompressedHeaderBlock(payload_length, compressed_size);
+  }
+
   return new_frame.release();
 }