QUIC - add instrumentation to HPACK.

net/spdy/hpack/hpack_encoder.h

Index: net/spdy/hpack/hpack_encoder.h
diff --git a/net/spdy/hpack/hpack_encoder.h b/net/spdy/hpack/hpack_encoder.h
index cd6558bb1e7f09539598bd04e803158ae3b1e27d..cfa6e0853eb6b617c67432192404a1a18f0f393c 100644
--- a/net/spdy/hpack/hpack_encoder.h
+++ b/net/spdy/hpack/hpack_encoder.h
@@ -58,6 +58,11 @@ class NET_EXPORT_PRIVATE HpackEncoder {
     return header_table_.settings_size_bound();
   }
 
+  void SetHeaderTableDebugVisitor(
+      std::unique_ptr<HpackHeaderTable::DebugVisitorInterface> visitor) {
+    header_table_.set_debug_visitor(std::move(visitor));
+  }
+
  private:
   typedef std::pair<base::StringPiece, base::StringPiece> Representation;
   typedef std::vector<Representation> Representations;