src/: Update the remaining include paths of string_split.h to its new location.

ppapi/proxy/file_chooser_resource.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 "ppapi/proxy/file_chooser_resource.h"
 
 #include "base/bind.h"
-#include "base/string_split.h"
+#include "base/strings/string_split.h"
 #include "ipc/ipc_message.h"
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/proxy/dispatch_reply_message.h"
 #include "ppapi/proxy/ppapi_messages.h"
 #include "ppapi/proxy/ppb_file_ref_proxy.h"
 #include "ppapi/shared_impl/var.h"
 
 namespace ppapi {
 namespace proxy {
 
@@ skipping 121 matching lines @@
         mode_ == PP_FILECHOOSERMODE_OPENMULTIPLE,
         sugg_str ? sugg_str->value() : std::string(),
         accept_types_);
   Call<PpapiPluginMsg_FileChooser_ShowReply>(RENDERER, msg,
       base::Bind(&FileChooserResource::OnPluginMsgShowReply, this));
   return PP_OK_COMPLETIONPENDING;
 }
 
 }  // namespace proxy
 }  // namespace ppapi