Improve documentation of potential memory leaks in URLMatcherFactory

chrome/common/extensions/matcher/url_matcher_factory.h

 // 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.
 
 #ifndef CHROME_COMMON_EXTENSIONS_MATCHER_URL_MATCHER_FACTORY_H_
 #define CHROME_COMMON_EXTENSIONS_MATCHER_URL_MATCHER_FACTORY_H_
 #pragma once
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "chrome/common/extensions/matcher/url_matcher.h"
 
 namespace base {
 class DictionaryValue;
 class Value;
 }
 
 namespace extensions {
 
 class URLMatcherFactory {
  public:
   // Creates a URLMatcherConditionSet from a UrlFilter dictionary as defined in
   // the declarative API. |url_fetcher_dict| contains the dictionary passed
   // by the extension, |id| is the identifier assigned to the created
   // URLMatcherConditionSet. In case of an error, |error| is set to contain
   // an error message.
+  //
+  // Note: In case this function fails or if you don't register the
+  // URLMatcherConditionSet to the URLMatcher, you need to call
+  // URLMatcher::ClearUnusedConditionSets() on the URLMatcher that owns this
+  // URLMatcherFactory. Otherwise you leak memory.
   static scoped_refptr<URLMatcherConditionSet> CreateFromURLFilterDictionary(
       URLMatcherConditionFactory* url_matcher_condition_factory,
       const base::DictionaryValue* url_filter_dict,
       URLMatcherConditionSet::ID id,
       std::string* error);
 
  private:
   // Returns whether a condition attribute with name |condition_attribute_name|
   // needs to be handled by the URLMatcher.
   static bool IsURLMatcherConditionAttribute(
@@ skipping 11 matching lines @@
 
   static scoped_ptr<URLMatcherPortFilter> CreateURLMatcherPorts(
       const base::Value* value, std::string* error);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(URLMatcherFactory);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_MATCHER_URL_MATCHER_FACTORY_H_