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

net/spdy/spdy_test_util_spdy3.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_SPDY_SPDY_TEST_UTIL_SPDY3_H_
 #define NET_SPDY_SPDY_TEST_UTIL_SPDY3_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 #include "crypto/ec_private_key.h"
 #include "crypto/ec_signature_creator.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/request_priority.h"
 #include "net/cert/cert_verifier.h"
 #include "net/dns/mock_host_resolver.h"
 #include "net/http/http_auth_handler_factory.h"
 #include "net/http/http_cache.h"
 #include "net/http/http_network_layer.h"
 #include "net/http/http_network_session.h"
@@ skipping 364 matching lines @@
   SpdySessionPool* const pool_;
 
   DISALLOW_COPY_AND_ASSIGN(SpdySessionPoolPeer);
 };
 
 }  // namespace test_spdy3
 
 }  // namespace net
 
 #endif  // NET_SPDY_SPDY_TEST_UTIL_SPDY3_H_