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

components/ssl_errors/error_classification.cc

Index: components/ssl_errors/error_classification.cc
diff --git a/components/ssl_errors/error_classification.cc b/components/ssl_errors/error_classification.cc
index da10872be4252f8cff83ccfb84b6323db53fb768..c8ba362778c634b65edaf134ab7d30c7051cc817 100644
--- a/components/ssl_errors/error_classification.cc
+++ b/components/ssl_errors/error_classification.cc
@@ -294,8 +294,8 @@ bool GetWWWSubDomainMatch(const GURL& request_url,
           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;
         }