Use a direct include of strings headers in chrome/browser/ui/cocoa/.

chrome/browser/ui/cocoa/omnibox/omnibox_view_mac.mm

 // 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 "chrome/browser/ui/cocoa/omnibox/omnibox_view_mac.h"
 
 #include <Carbon/Carbon.h>  // kVK_Return
 
 #include "base/mac/foundation_util.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/autocomplete/autocomplete_input.h"
 #include "chrome/browser/autocomplete/autocomplete_match.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/search/search.h"
 #include "chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_cell.h"
 #import "chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_editor.h"
 #include "chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.h"
 #include "chrome/browser/ui/omnibox/omnibox_edit_controller.h"
@@ skipping 945 matching lines @@
 
 NSUInteger OmniboxViewMac::GetTextLength() const {
   return [field_ currentEditor] ?  [[[field_ currentEditor] string] length] :
                                    [[field_ stringValue] length];
 }
 
 bool OmniboxViewMac::IsCaretAtEnd() const {
   const NSRange selection = GetSelectedRange();
   return NSMaxRange(selection) == GetTextLength();
 }