Invert host/domain checks in SameDomainOrHost

net/base/registry_controlled_domains/registry_controlled_domain.cc

Index: net/base/registry_controlled_domains/registry_controlled_domain.cc
diff --git a/net/base/registry_controlled_domains/registry_controlled_domain.cc b/net/base/registry_controlled_domains/registry_controlled_domain.cc
index 493ea68678b0b2a11d1817f42eefa33328894dc2..e1e24907a08cd080baa29781279d32c166a56ebb 100644
--- a/net/base/registry_controlled_domains/registry_controlled_domain.cc
+++ b/net/base/registry_controlled_domains/registry_controlled_domain.cc
@@ -329,6 +329,15 @@ bool SameDomainOrHost(
     const GURL& gurl1,
     const GURL& gurl2,
     PrivateRegistryFilter filter) {
+  // First, check if the hosts are identical.
+  const url::Component host1 = gurl1.parsed_for_possibly_invalid_spec().host;
+  const url::Component host2 = gurl2.parsed_for_possibly_invalid_spec().host;
+  if ((host1.len > 0) && (host1.len == host2.len) &&
+      !strncmp(gurl1.possibly_invalid_spec().data() + host1.begin,
+               gurl2.possibly_invalid_spec().data() + host2.begin, host1.len)) {
+    return true;
+  }
+
   // See if both URLs have a known domain + registry, and those values are the
   // same.
   const base::StringPiece domain1 =
@@ -337,15 +346,7 @@ bool SameDomainOrHost(
       GetDomainAndRegistryAsStringPiece(gurl2, filter);
   if (!domain1.empty() || !domain2.empty())
     return domain1 == domain2;
-
-  // No domains.  See if the hosts are identical.
-  const url::Component host1 = gurl1.parsed_for_possibly_invalid_spec().host;
-  const url::Component host2 = gurl2.parsed_for_possibly_invalid_spec().host;
-  if ((host1.len <= 0) || (host1.len != host2.len))
-    return false;
-  return !strncmp(gurl1.possibly_invalid_spec().data() + host1.begin,
-                  gurl2.possibly_invalid_spec().data() + host2.begin,
-                  host1.len);
+  return false;

[Peter Kasting, 2016/11/14 23:00:25]

I think a slightly faster, and hopefully more readable, implementation of this
function would be:

  // Quickly reject cases where either host is empty.
  if (!gurl1.has_host() || !gurl2.has_host())
    return false;

  // Check for exact host matches, which is faster than looking up the domain
  // and registry.
  if (gurl1.host_piece() == gurl2.host_piece())
    return true;

  // Check for a domain and registry match.
  const auto domain1 = GetDomainAndRegistryAsStringPiece(gurl1, filter);
  return !domain1.empty() &&
         (domain1 == GetDomainAndRegistryAsStringPiece(gurl2, filter));

 }
 
 bool SameDomainOrHost(const url::Origin& origin1,