URL Formatter: Add StripSubdomain method that preserves eTLD + 1.

components/ssl_errors/error_classification.cc

 // 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.
 
 #include "components/ssl_errors/error_classification.h"
 
 #include <limits.h>
 #include <stddef.h>
 
 #include <vector>
@@ skipping 276 matching lines @@
           dns_name.length() == host_name.length() ||
           !HostNameHasKnownTLD(dns_name)) {
         continue;
       } else if (dns_name.length() > host_name.length()) {
         if (url_formatter::StripWWW(base::ASCIIToUTF16(dns_name)) ==
             base::ASCIIToUTF16(host_name)) {
           *www_match_host_name = dns_name;
           return true;
         }
       } else {
-        if (url_formatter::StripWWW(base::ASCIIToUTF16(host_name)) ==
-            base::ASCIIToUTF16(dns_name)) {
+        if (url_formatter::StripSubdomains(
+                request_url, url_formatter::kStripWWW) == dns_name) {
           *www_match_host_name = dns_name;
           return true;
         }
       }
     }
   }
   return false;
 }
 
 bool NameUnderAnyNames(const HostnameTokens& child,
@@ skipping 155 matching lines @@
   return std::find(dns_names_domain.begin(), dns_names_domain.end() - 1,
                    host_name_domain) != dns_names_domain.end() - 1;
 }
 
 bool IsHostnameNonUniqueOrDotless(const std::string& hostname) {
   return net::IsHostnameNonUnique(hostname) ||
          hostname.find('.') == std::string::npos;
 }
 
 }  // namespace ssl_errors