Modify SpdyHeaderBlock's internals to consolidate header values only on first access.

net/base/arena.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/base/arena.h"
 
 #include <string.h>
 
 #include <algorithm>
 
@@ skipping 50 matching lines @@
   Block& b = blocks_.back();
   if (size <= b.used && data + size == b.data.get() + b.used) {
     // The memory region passed by the caller was the most recent allocation
     // from the final block in this arena.
     b.used -= size;
   }
 }
 
 void UnsafeArena::Reset() {
   blocks_.clear();
+  status_.bytes_allocated_ = 0;
 }
 
 void UnsafeArena::Reserve(size_t additional_space) {
   if (blocks_.empty()) {
     AllocBlock(std::max(additional_space, block_size_));
   } else {
     const Block& last = blocks_.back();
     if (last.size < last.used + additional_space) {
       AllocBlock(std::max(additional_space, block_size_));
     }
   }
 }
 
 void UnsafeArena::AllocBlock(size_t size) {
   blocks_.push_back(Block(size));
+  status_.bytes_allocated_ += size;
 }
 
 UnsafeArena::Block::Block(size_t s) : data(new char[s]), size(s), used(0) {}
 
 UnsafeArena::Block::~Block() {}
 
 UnsafeArena::Block::Block(UnsafeArena::Block&& other)
     : size(other.size), used(other.used) {
   data = std::move(other.data);
 }
 
 UnsafeArena::Block& UnsafeArena::Block::operator=(UnsafeArena::Block&& other) {
   size = other.size;
   used = other.used;
   data = std::move(other.data);
   return *this;
 }
 
 }  // namespace net