Revert of Move JoinString to the base namespace

extensions/browser/api/bluetooth/bluetooth_private_api.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 "extensions/browser/api/bluetooth/bluetooth_private_api.h"
 
 #include "base/callback.h"
 #include "base/lazy_instance.h"
 #include "base/strings/string_util.h"
 #include "device/bluetooth/bluetooth_adapter.h"
@@ skipping 209 matching lines @@
 void BluetoothPrivateSetAdapterStateFunction::SendError() {
   DCHECK(pending_properties_.empty());
   DCHECK(!failed_properties_.empty());
 
   std::vector<std::string> failed_vector;
   std::copy(failed_properties_.begin(),
             failed_properties_.end(),
             std::back_inserter(failed_vector));
 
   std::vector<std::string> replacements(1);
-  replacements[0] = base::JoinString(failed_vector, ", ");
+  replacements[0] = JoinString(failed_vector, ", ");
   std::string error =
       ReplaceStringPlaceholders(kSetAdapterPropertyError, replacements, NULL);
   SetError(error);
   SendResponse(false);
 }
 
 BluetoothPrivateSetPairingResponseFunction::
     BluetoothPrivateSetPairingResponseFunction() {}
 
 BluetoothPrivateSetPairingResponseFunction::
@@ skipping 170 matching lines @@
               this),
           base::Bind(
               &BluetoothPrivateSetDiscoveryFilterFunction::OnErrorCallback,
               this));
   return true;
 }
 
 }  // namespace core_api
 
 }  // namespace extensions