Implement correct logic for URLPatternSet set operators.

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 da6ad132db183433d726363f5d291b9e412e0158..39db9e241ac033dd1dddb5cef4c947b19615e4b3 100644
--- a/extensions/common/url_pattern_set.h
+++ b/extensions/common/url_pattern_set.h
@@ -96,6 +96,9 @@ class URLPatternSet {
                 std::string* error);
 
  private:
+  // Inserts a pattern in the set without pattern containment normalization.
+  bool InsertPattern(const URLPattern& pattern);
+
   // The list of URL patterns that comprise the extent.
   std::set<URLPattern> patterns_;
 };