Provide the equivalent of GURL::DomainIs for url::Origin.

url/origin.h

Index: url/origin.h
diff --git a/url/origin.h b/url/origin.h
index aab1f05a2013cc84cd4aedbb91a9e10b0df88307..9ac777949a4c1922b8e91e97cc2b2f898fb31858 100644
--- a/url/origin.h
+++ b/url/origin.h
@@ -122,6 +122,9 @@ class URL_EXPORT Origin {
     return IsSameOriginWith(other);
   }
 
+  // Same as GURL::DomainIs. If |this| origin is unique, then returns false.
+  bool DomainIs(base::StringPiece lower_ascii_domain) const;
+
   // Allows Origin to be used as a key in STL (for example, a std::set or
   // std::map).
   bool operator<(const Origin& other) const;