Improve documentation of potential memory leaks in URLMatcherFactory

chrome/common/extensions/matcher/url_matcher_factory.h

Index: chrome/common/extensions/matcher/url_matcher_factory.h
diff --git a/chrome/common/extensions/matcher/url_matcher_factory.h b/chrome/common/extensions/matcher/url_matcher_factory.h
index 138281430328e99a22cb84591859ea18bbbcd5a1..ade3508326523decb0f82ead565a11ee53553911 100644
--- a/chrome/common/extensions/matcher/url_matcher_factory.h
+++ b/chrome/common/extensions/matcher/url_matcher_factory.h
@@ -25,6 +25,11 @@ class URLMatcherFactory {
   // 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,