Adds a DebugString() method to QuicHeaderList.

net/quic/quic_header_list.cc

 // Copyright (c) 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_header_list.h"
 
 namespace net {
 
 QuicHeaderList::QuicHeaderList() : uncompressed_header_bytes_(0) {}
 
@@ skipping 19 matching lines @@
 
 void QuicHeaderList::OnHeaderBlockEnd(size_t uncompressed_header_bytes) {
   uncompressed_header_bytes_ = uncompressed_header_bytes;
 }
 
 void QuicHeaderList::Clear() {
   header_list_.clear();
   uncompressed_header_bytes_ = 0;
 }
 
+std::string QuicHeaderList::DebugString() const {
+  std::string s = "{ ";
+  for (const auto& p : *this) {
+    s.append(p.first + "=" + p.second + ", ");
+  }
+  s.append("}");
+  return s;
+}
+
 }  // namespace net