Constify SchemeHostPort and Origin accessors.

url/origin.h

 // Copyright 2015 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 URL_ORIGIN_H_
 #define URL_ORIGIN_H_
 
 #include <string>
 
 #include "base/strings/string16.h"
@@ skipping 71 matching lines @@
   //
   // 1. If |url| is invalid or non-standard, a unique Origin is constructed.
   // 2. 'filesystem' URLs behave as 'blob' URLs (that is, the origin is parsed
   //    out of everything in the URL which follows the scheme).
   // 3. 'file' URLs all parse as ("file", "", 0).
   explicit Origin(const GURL& url);
 
   ~Origin();
 
   // For unique origins, these return ("", "", 0).
-  //
-  // TODO(mkwst): These should be 'const std::string&', along with their
-  // 'url::SchemeHostPort' analogs.
-  std::string scheme() const { return tuple_.scheme(); }
-  std::string host() const { return tuple_.host(); }
+  const std::string& scheme() const { return tuple_.scheme(); }
+  const std::string& host() const { return tuple_.host(); }
   uint16 port() const { return tuple_.port(); }
 
   bool unique() const { return unique_; }
 
   // An ASCII serialization of the Origin as per Section 6.2 of RFC 6454, with
   // the addition that all Origins with a 'file' scheme serialize to "file://".
   std::string Serialize() const;
 
   // Two Origins are "same-origin" if their schemes, hosts, and ports are exact
   // matches; and neither is unique.
   bool IsSameOriginWith(const Origin& other) const;
 
   // Allows SchemeHostPort to used as a key in STL (for example, a std::set or
   // std::map).
   bool operator<(const Origin& other) const;
 
  private:
   SchemeHostPort tuple_;
   bool unique_;
 
   DISALLOW_COPY_AND_ASSIGN(Origin);
 };
 
 URL_EXPORT std::ostream& operator<<(std::ostream& out,
                                     const Origin& origin);
 
 }  // namespace url
 
 #endif  // URL_SCHEME_HOST_PORT_H_