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

ui/gfx/font_fallback_win.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 "ui/gfx/font_fallback_win.h"
 
 #include <map>
 
 #include "base/memory/singleton.h"
-#include "base/string_split.h"
 #include "base/string_util.h"
+#include "base/strings/string_split.h"
 #include "base/utf_string_conversions.h"
 #include "base/win/registry.h"
 #include "ui/gfx/font.h"
 
 namespace gfx {
 
 namespace {
 
 // Queries the registry to get a mapping from font filenames to font names.
 void QueryFontsFromRegistry(std::map<std::string, std::string>* map) {
@@ skipping 212 matching lines @@
   // Note: One possibility would be to always merge both lists of fonts,
   //       but it is not clear whether there are any real world scenarios
   //       where this would actually help.
   if (fonts->empty())
     fonts = font_link->GetLinkedFonts(current_font_);
 
   return fonts;
 }
 
 }  // namespace gfx