Constify SchemeHostPort and Origin accessors.

url/scheme_host_port.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_SCHEME_HOST_PORT_H_
 #define URL_SCHEME_HOST_PORT_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 78 matching lines @@
   //
   // If |url| is invalid or non-standard, the result will be an invalid
   // SchemeHostPort object.
   explicit SchemeHostPort(const GURL& url);
 
   ~SchemeHostPort();
 
   // Returns the host component, in URL form. That is all IDN domain names will
   // be expressed as A-Labels ('☃.net' will be returned as 'xn--n3h.net'), and
   // and all IPv6 addresses will be enclosed in brackets ("[2001:db8::1]").
-  std::string host() const { return host_; }
-  std::string scheme() const { return scheme_; }
+  const std::string& host() const { return host_; }
+  const std::string& scheme() const { return scheme_; }
   uint16 port() const { return port_; }
   bool IsInvalid() const;
 
   // Serializes the SchemeHostPort tuple to a canonical form.
   //
   // While this string form resembles the Origin serialization specified in
   // Section 6.2 of RFC 6454, it is important to note that invalid
   // SchemeHostPort tuples serialize to the empty string, rather than being
   // serialized as a unique Origin.
   std::string Serialize() const;
@@ skipping 12 matching lines @@
 
  private:
   std::string scheme_;
   std::string host_;
   uint16 port_;
 };
 
 }  // namespace url
 
 #endif  // URL_SCHEME_HOST_PORT_H_