Use a direct include of strings headers in ppapi/, printing/.

ppapi/proxy/ppp_messaging_proxy_perftest.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 "base/command_line.h"
 #include "base/perftimer.h"
-#include "base/string_number_conversions.h"
+#include "base/strings/string_number_conversions.h"
 #include "ppapi/c/ppp_messaging.h"
 #include "ppapi/proxy/ppapi_proxy_test.h"
 #include "ppapi/proxy/serialized_var.h"
 #include "ppapi/shared_impl/ppapi_globals.h"
 #include "ppapi/shared_impl/var.h"
 #include "ppapi/shared_impl/var_tracker.h"
 
 namespace ppapi {
 namespace proxy {
 namespace {
@@ skipping 61 matching lines @@
     PP_Var host_string = StringVar::StringToPPVar(test_string);
     ppp_messaging->HandleMessage(kTestInstance, host_string);
     handle_message_called.Wait();
     PpapiGlobals::Get()->GetVarTracker()->ReleaseVar(host_string);
   }
 }
 
 }  // namespace proxy
 }  // namespace ppapi