Change uses of base::JoinString to pass StringPieces where possible.

components/search_engines/keyword_table.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 "components/search_engines/keyword_table.h"
 
 #include <stddef.h>
 
 #include <memory>
 #include <set>
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "components/history/core/browser/url_database.h"
 #include "components/search_engines/search_terms_data.h"
 #include "components/search_engines/template_url.h"
 #include "components/webdata/common/web_database.h"
 #include "sql/statement.h"
 #include "sql/transaction.h"
 #include "url/gurl.h"
 
 using base::Time;
 
 // static
 const char KeywordTable::kDefaultSearchProviderKey[] =
     "Default Search Provider ID";
 
 namespace {
 
 // Keys used in the meta table.
 const char kBuiltinKeywordVersion[] = "Builtin Keyword Version";
 
 const std::string ColumnsForVersion(int version, bool concatenated) {
-  std::vector<std::string> columns;
+  std::vector<base::StringPiece> columns;
 
   columns.push_back("id");
   columns.push_back("short_name");
   columns.push_back("keyword");
   columns.push_back("favicon_url");
   columns.push_back("url");
   columns.push_back("safe_for_autoreplace");
   columns.push_back("originating_url");
   columns.push_back("date_created");
   columns.push_back("usage_count");
@@ skipping 402 matching lines @@
                                    << ", ignoring.";
     return true;
   }
 
   if (!s.Succeeded())
     return false;
 
   *result = s.ColumnString(0);
   return true;
 }