Factor out SameHost() in registry_controlled_domains

net/base/registry_controlled_domains/registry_controlled_domain.h

 // Copyright (c) 2012 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.
 
 // NB: Modelled after Mozilla's code (originally written by Pamela Greene,
 // later modified by others), but almost entirely rewritten for Chrome.
 //   (netwerk/dns/src/nsEffectiveTLDService.h)
 /* ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  *
@@ skipping 177 matching lines @@
 // std::string-returning version. Update clients.
 NET_EXPORT base::StringPiece GetDomainAndRegistryAsStringPiece(
     const GURL& gurl,
     PrivateRegistryFilter filter);
 
 // Like the GURL version, but takes a host (which is canonicalized internally)
 // instead of a full GURL.
 NET_EXPORT std::string GetDomainAndRegistry(base::StringPiece host,
                                             PrivateRegistryFilter filter);
 
+// Returns whether the hosts of the GURLs are identical.

[engedy, 2016/10/21 08:43:22]

nit: Maybe we could put this into the anonymous namespace as well, and only move
the declaration to the header once we actually start using it?

When we do that, we should clarify in one more line what identical means in this
context.

+NET_EXPORT bool SameHost(const GURL& gurl1, const GURL& gurl2);
+
 // These convenience functions return true if the two GURLs or Origins both have
 // hosts and one of the following is true:
 // * They each have a known domain and registry, and it is the same for both
 //   URLs.  Note that this means the trailing dot, if any, must match too.
-// * They don't have known domains/registries, but the hosts are identical.
+// * They don't have known domains/registries, but the hosts are identical
+//   (determined by the SameHost function above).
 // Effectively, callers can use this function to check whether the input URLs
 // represent hosts "on the same site".
 NET_EXPORT bool SameDomainOrHost(const GURL& gurl1, const GURL& gurl2,
                                  PrivateRegistryFilter filter);
 NET_EXPORT bool SameDomainOrHost(const url::Origin& origin1,
                                  const url::Origin& origin2,
                                  PrivateRegistryFilter filter);
 
 // Finds the length in bytes of the registrar portion of the host in the
 // given GURL.  Returns std::string::npos if the GURL is invalid or has no
@@ skipping 33 matching lines @@
 // Used for unit tests. Use default domains.
 NET_EXPORT_PRIVATE void SetFindDomainGraph();
 
 // Used for unit tests, so that a frozen list of domains is used.
 NET_EXPORT_PRIVATE void SetFindDomainGraph(const unsigned char* domains,
                                            size_t length);
 }  // namespace registry_controlled_domains
 }  // namespace net
 
 #endif  // NET_BASE_REGISTRY_CONTROLLED_DOMAINS_REGISTRY_CONTROLLED_DOMAIN_H_