Add stream operators for URLPattern and URLPatternSet and unit test for URLPatternSet

extensions/common/url_pattern_set.h

Index: extensions/common/url_pattern_set.h
diff --git a/extensions/common/url_pattern_set.h b/extensions/common/url_pattern_set.h
index 0cab66740ccc9effadc6dfd581d6da5b3c601440..ed2163f566ffa49a9aeeb9df36c61fb433a18cf0 100644
--- a/extensions/common/url_pattern_set.h
+++ b/extensions/common/url_pattern_set.h
@@ -100,6 +100,9 @@ class URLPatternSet {
   std::set<URLPattern> patterns_;
 };
 
+std::ostream& operator<<(std::ostream& out,
+                         const URLPatternSet& url_pattern_set);
+
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_URL_PATTERN_SET_H_