Use a direct include of strings headers in rlz/, sandbox/, skia/, sql/, sync/.

sync/test/engine/test_id_factory.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.
 //
 // A tool making it easier to create IDs for unit testing.
 
 #ifndef SYNC_TEST_ENGINE_TEST_ID_FACTORY_H_
 #define SYNC_TEST_ENGINE_TEST_ID_FACTORY_H_
 
 #include <string>
 
-#include "base/string_number_conversions.h"
+#include "base/strings/string_number_conversions.h"
 #include "sync/syncable/syncable_id.h"
 
 namespace syncer {
 
 class TestIdFactory {
  public:
   TestIdFactory() : next_value_(1337000) {}
   ~TestIdFactory() {}
 
   // Get the root ID.
@@ skipping 40 matching lines @@
   int next_value() {
     return next_value_++;
   }
   int next_value_;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_TEST_ENGINE_TEST_ID_FACTORY_H_