Revert of Move JoinString to the base namespace

components/proximity_auth/cryptauth/cryptauth_gcm_manager_impl.cc

 // Copyright 2015 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 "components/proximity_auth/cryptauth/cryptauth_gcm_manager_impl.h"
 
 #include "base/bind.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/string_util.h"
 #include "components/gcm_driver/gcm_driver.h"
@@ skipping 75 matching lines @@
 void CryptAuthGCMManagerImpl::OnMessage(const std::string& app_id,
                                         const gcm::IncomingMessage& message) {
   std::vector<std::string> fields;
   for (const auto& kv : message.data) {
     fields.push_back(std::string(kv.first) + ": " + std::string(kv.second));
   }
 
   PA_LOG(INFO) << "GCM message received:\n"
                << "  sender_id: " << message.sender_id << "\n"
                << "  collapse_key: " << message.collapse_key << "\n"
-               << "  data:\n    " << base::JoinString(fields, "\n    ");
+               << "  data:\n    " << JoinString(fields, "\n    ");
 
   if (message.data.find(kRegistrationTickleTypeKey) == message.data.end()) {
     PA_LOG(WARNING) << "GCM message does not contain 'registrationTickleType'.";
   } else {
     std::string tickle_type = message.data.at(kRegistrationTickleTypeKey);
     if (tickle_type == kRegistrationTickleTypeForceEnrollment ||
         tickle_type == kRegistrationTickleTypeUpdateEnrollment) {
       // These tickle types correspond to re-enrollment messages.
       FOR_EACH_OBSERVER(Observer, observers_, OnReenrollMessage());
     } else if (tickle_type == kRegistrationTickleTypeDevicesSync) {
@@ skipping 30 matching lines @@
     return;
   }
 
   PA_LOG(INFO) << "GCM registration success, registration_id="
                << registration_id;
   pref_service_->SetString(prefs::kCryptAuthGCMRegistrationId, registration_id);
   FOR_EACH_OBSERVER(Observer, observers_, OnGCMRegistrationResult(true));
 }
 
 }  // namespace proximity_auth