Use a direct include of strings headers, delete some strings forwarding headers.

net/http/http_response_headers.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 NET_HTTP_HTTP_RESPONSE_HEADERS_H_
 #define NET_HTTP_HTTP_RESPONSE_HEADERS_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/containers/hash_tables.h"
 #include "base/memory/ref_counted.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 #include "net/base/net_export.h"
 #include "net/base/net_log.h"
 #include "net/http/http_version.h"
 
 class Pickle;
 class PickleIterator;
 
 namespace base {
 class Time;
 class TimeDelta;
@@ skipping 343 matching lines @@
 
   // The parsed http version number (not normalized).
   HttpVersion parsed_http_version_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpResponseHeaders);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_RESPONSE_HEADERS_H_