Avoid unnecessary std::string allocations.

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 164 matching lines @@
 //   http://a.b.co.uk/file.html      -> "b.co.uk"     (co.uk)
 //   file:///C:/bar.html             -> ""            (no host)
 //   http://foo.com../file.html      -> ""            (multiple trailing dots)
 //   http://192.168.0.1/file.html    -> ""            (IP address)
 //   http://bar/file.html            -> ""            (no subcomponents)
 //   http://co.uk/file.html          -> ""            (host is a registry)
 //   http://foo.bar/file.html        -> "foo.bar"     (no rule; assume bar)
 NET_EXPORT std::string GetDomainAndRegistry(const GURL& gurl,
                                             PrivateRegistryFilter filter);
 
+// Same as above, but returns a part of |gurl|'s host in a StringPiece.

[engedy, 2016/09/28 17:22:52]

Phrasing nit: ... returns the domain and registry as a StringPiece that
references the underlying string of the passed-in |gurl|.

[pkalinnikov, 2016/10/05 11:51:35]

Done.

+// TODO(pkalinnikov): Rename this to GetDomainAndRegistry and get rid of the

[engedy, 2016/09/28 17:22:52]

As discussed, please run some quick tests to see how often this is called during
normal browsing, e.g. by adding TRACE_EVENT inside.

If called often, I agree that we should file a bug documenting that fact,
reference that bug here in this CL, then update all existing call sites in a
follow-up CL and remove this TODO.

[pkalinnikov, 2016/10/05 11:51:35]

It is used not frequently during normal browsing. In a small experiment I
collected 9 calls, which was roughly the number of times I clicked some
hyperlink.

Can I leave the TODO?

[engedy, 2016/10/05 11:58:14]

Usually it's recommended to leave a TODO only if we are actually planning to do
this refactor in the near future, and in that case we should file a bug to track
it.

I'd leave it up to Peter to decide if the refactor is worth it in light of how
rarely this is called.

+// 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);
 
 // 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.
@@ skipping 43 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_