HPACK optimal Huffman code instrumentation and UMA collection.

net/spdy/hpack_encoder.h

Index: net/spdy/hpack_encoder.h
diff --git a/net/spdy/hpack_encoder.h b/net/spdy/hpack_encoder.h
index 12fa8b458740ba10bf5a287b02a47d39e64decf8..6458cad5e4b8efb1fb924fc5ff3186dd091338fd 100644
--- a/net/spdy/hpack_encoder.h
+++ b/net/spdy/hpack_encoder.h
@@ -35,13 +35,24 @@ class NET_EXPORT_PRIVATE HpackEncoder {
   bool EncodeHeaderSet(const std::map<std::string, std::string>& header_set,
                        std::string* output);
 
+  // Sets externally-owned storage for aggregating character counts of emitted
+  // literal representations.
+  void SetCharCountsStorage(std::vector<size_t>* char_counts,
+                            size_t* total_char_counts);
+
  private:
   static void CookieToCrumbs(base::StringPiece cookie,
                              std::vector<base::StringPiece>* out);
 
+  void UpdateCharacterCounts(base::StringPiece str);
+
   uint32 max_string_literal_size_;
   HpackEncodingContext context_;
 
+  // Externally-owned, nullable storage for character counts of literals.
+  std::vector<size_t>* char_counts_;
+  size_t* total_char_counts_;
+
   DISALLOW_COPY_AND_ASSIGN(HpackEncoder);
 };