net: Update the include paths of base/string_piece.h to its new location.

net/tools/quic/quic_in_memory_cache.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_TOOLS_QUIC_QUIC_IN_MEMORY_CACHE_H_
 #define NET_TOOLS_QUIC_QUIC_IN_MEMORY_CACHE_H_
 
 #include <string>
 
 #include "base/hash_tables.h"
 #include "base/memory/singleton.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 #include "net/tools/flip_server/balsa_frame.h"
 #include "net/tools/flip_server/balsa_headers.h"
 
 template <typename T> struct DefaultSingletonTraits;
 
 namespace net {
 namespace tools {
 
 class QuicServer;
 
@@ skipping 53 matching lines @@
   // Cached responses.
   ResponseMap responses_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicInMemoryCache);
 };
 
 }  // namespace tools
 }  // namespace net
 
 #endif  // NET_TOOLS_QUIC_QUIC_IN_MEMORY_CACHE_H_