Revert of Move JoinString to the base namespace

chrome/browser/sync/profile_sync_service_android_unittest.cc

 // Copyright 2014 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 <algorithm>
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string_util.h"
@@ skipping 79 matching lines @@
 
   std::vector<std::string> invalidation_names;
   for (syncer::ModelTypeSet::Iterator it = model_types.First(); it.Good();
        it.Inc()) {
     std::string notification_type;
     if (syncer::RealModelTypeToNotificationType(it.Get(), &notification_type))
       invalidation_names.push_back(notification_type);
   }
 
   std::sort(invalidation_names.begin(), invalidation_names.end());
-  EXPECT_EQ(base::JoinString(invalidation_names, ", "),
+  EXPECT_EQ(JoinString(invalidation_names, ", "),
             ProfileSyncServiceAndroid::ModelTypeSelectionToStringForTest(
                 model_type_selection));
 }