Use a direct include of strings headers in chrome/browser/extensions/, part 4.

chrome/browser/extensions/extensions_quota_service_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 "base/message_loop.h"
 #include "base/process.h"
 #include "base/stl_util.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "chrome/browser/extensions/extension_function.h"
 #include "chrome/browser/extensions/extensions_quota_service.h"
 #include "content/public/test/test_browser_thread.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using base::TimeDelta;
 using base::TimeTicks;
 using content::BrowserThread;
 
 typedef QuotaLimitHeuristic::Bucket Bucket;
@@ skipping 387 matching lines @@
   // wait a while.
   EXPECT_NE(
       "",
       service_->Assess(
           extension_a_, f.get(), &arg, kStartTime + TimeDelta::FromDays(1)));
   EXPECT_NE(
       "",
       service_->Assess(
           extension_a_, g.get(), &arg, kStartTime + TimeDelta::FromDays(1)));
 }