Use a direct include of strings headers in remoting/.

remoting/host/heartbeat_sender_unittest.cc

 // 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.
 
 #include "remoting/host/heartbeat_sender.h"
 
 #include <set>
 
 #include "base/memory/ref_counted.h"
 #include "base/message_loop.h"
 #include "base/message_loop/message_loop_proxy.h"
-#include "base/string_number_conversions.h"
+#include "base/strings/string_number_conversions.h"
 #include "remoting/base/constants.h"
 #include "remoting/base/rsa_key_pair.h"
 #include "remoting/base/test_rsa_key_pair.h"
 #include "remoting/jingle_glue/iq_sender.h"
 #include "remoting/jingle_glue/mock_objects.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/libjingle/source/talk/xmllite/xmlelement.h"
 #include "third_party/libjingle/source/talk/xmpp/constants.h"
 
@@ skipping 215 matching lines @@
   EXPECT_TRUE(heartbeat_stanza->NextNamed(signature_tag) == NULL);
 
   scoped_refptr<RsaKeyPair> key_pair = RsaKeyPair::FromString(kTestRsaKeyPair);
   ASSERT_TRUE(key_pair.get());
   std::string expected_signature =
       key_pair->SignMessage(std::string(kTestJid) + ' ' + expectedSequenceId);
   EXPECT_EQ(expected_signature, signature->BodyText());
 }
 
 }  // namespace remoting