Coverity: Fix a few pass-by-values.

chrome/browser/extensions/api/declarative/initializing_rules_registry.cc

 // Copyright (c) 2012 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 "chrome/browser/extensions/api/declarative/initializing_rules_registry.h"
 
 #include "base/logging.h"
 #include "base/stringprintf.h"
 #include "base/values.h"
 #include "chrome/browser/extensions/api/declarative/declarative_api_constants.h"
@@ skipping 67 matching lines @@
     const std::string& extension_id,
     const std::string& rule_id) const {
   RuleIdentifiersMap::const_iterator identifiers =
       used_rule_identifiers_.find(extension_id);
   if (identifiers == used_rule_identifiers_.end())
     return true;
   return identifiers->second.find(rule_id) == identifiers->second.end();
 }
 
 std::string InitializingRulesRegistry::GenerateUniqueId(
-    std::string extension_id) {
+    const std::string& extension_id) {
   while (!IsUniqueId(extension_id, ToId(last_generated_rule_identifier_id_)))
     ++last_generated_rule_identifier_id_;
   std::string new_id = ToId(last_generated_rule_identifier_id_);
   used_rule_identifiers_[extension_id].insert(new_id);
   return new_id;
 }
 
 void InitializingRulesRegistry::RemoveUsedRuleIdentifiers(
     const std::string& extension_id,
     const std::vector<std::string>& identifiers) {
@@ skipping 43 matching lines @@
     const std::vector<DictionaryValue*>& rules) {
   std::vector<DictionaryValue*>::const_iterator i;
   for (i = rules.begin(); i != rules.end(); ++i) {
     DictionaryValue* rule = *i;
     if (!rule->HasKey(keys::kPriority))
       rule->SetInteger(keys::kPriority, 100);
   }
 }
 
 }  // namespace extensions