Use a direct include of strings headers in base/.

base/pickle.h

 // 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.
 
 #ifndef BASE_PICKLE_H__
 #define BASE_PICKLE_H__
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "base/logging.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 
 class Pickle;
 
 // PickleIterator reads data from a Pickle. The Pickle object must remain valid
 // while the PickleIterator object is in use.
 class BASE_EXPORT PickleIterator {
  public:
   PickleIterator() : read_ptr_(NULL), read_end_ptr_(NULL) {}
   explicit PickleIterator(const Pickle& pickle);
 
@@ skipping 312 matching lines @@
   // Allocation size of payload (or -1 if allocation is const).
   size_t capacity_;
   size_t variable_buffer_offset_;  // IF non-zero, then offset to a buffer.
 
   FRIEND_TEST_ALL_PREFIXES(PickleTest, Resize);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNext);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNextWithIncompleteHeader);
 };
 
 #endif  // BASE_PICKLE_H__