base: Fix an inefficiency in base::Pickle that caused extraneous allocations.

base/pickle.cc

 // Copyright (c) 2012 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 "base/pickle.h"
 
 #include <stdlib.h>
 
 #include <algorithm>  // for max()
 
@@ skipping 236 matching lines @@
   // If there is anything wrong with the data, we're not going to use it.
   if (!header_size_)
     header_ = NULL;
 }
 
 Pickle::Pickle(const Pickle& other)
     : header_(NULL),
       header_size_(other.header_size_),
       capacity_after_header_(0),
       write_offset_(other.write_offset_) {
-  size_t payload_size = header_size_ + other.header_->payload_size;
-  Resize(payload_size);
-  memcpy(header_, other.header_, payload_size);
+  Resize(other.header_->payload_size);
+  memcpy(header_, other.header_, header_size_ + other.header_->payload_size);
 }
 
 Pickle::~Pickle() {
   if (capacity_after_header_ != kCapacityReadOnly)
     free(header_);
 }
 
 Pickle& Pickle::operator=(const Pickle& other) {
   if (this == &other) {
     NOTREACHED();
@@ skipping 110 matching lines @@
   }
 
   char* write = mutable_payload() + write_offset_;
   memcpy(write, data, length);
   memset(write + length, 0, data_len - length);
   header_->payload_size = static_cast<uint32>(new_size);
   write_offset_ = new_size;
 }
 
 }  // namespace base