Revert of Move JoinString to the base namespace

ui/app_list/search/history.cc

 // Copyright 2013 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 "ui/app_list/search/history.h"
 
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "ui/app_list/search/history_data.h"
 #include "ui/app_list/search/history_data_store.h"
 #include "ui/app_list/search/tokenized_string.h"
 
 namespace app_list {
 
 namespace {
 
 // Normalize the given string by joining all its tokens with a space.
 std::string NormalizeString(const std::string& utf8) {
   TokenizedString tokenized(base::UTF8ToUTF16(utf8));
-  return base::UTF16ToUTF8(
-      base::JoinString(tokenized.tokens(), base::ASCIIToUTF16(" ")));
+  return base::UTF16ToUTF8(JoinString(tokenized.tokens(), ' '));
 }
 
 }  // namespace
 
 History::History(scoped_refptr<HistoryDataStore> store)
     : store_(store), data_loaded_(false) {
   const size_t kMaxQueryEntries = 1000;
   const size_t kMaxSecondaryQueries = 5;
 
   data_.reset(
@@ skipping 19 matching lines @@
     const std::string& query) const {
   DCHECK(IsReady());
   return data_->GetKnownResults(NormalizeString(query)).Pass();
 }
 
 void History::OnHistoryDataLoadedFromStore() {
   data_loaded_ = true;
 }
 
 }  // namespace app_list