Implement a new IDN display policy

components/url_formatter/url_formatter.h

Index: components/url_formatter/url_formatter.h
diff --git a/components/url_formatter/url_formatter.h b/components/url_formatter/url_formatter.h
index ddf40985f659e42e0ca2d8b5740266f08add6f47..d460ba0e681874fd1903572313e5112e52bc1751 100644
--- a/components/url_formatter/url_formatter.h
+++ b/components/url_formatter/url_formatter.h
@@ -53,8 +53,9 @@ extern const FormatUrlType kFormatUrlOmitTrailingSlashOnBareHostname;
 // Convenience for omitting all unecessary types.
 extern const FormatUrlType kFormatUrlOmitAll;
 
-// Creates a string representation of |url|. The IDN host name may be in Unicode
-// if |languages| accepts the Unicode representation. |format_type| is a bitmask
+// Creates a string representation of |url|. The IDN host name is turned to
+// Unicode if the Unicode representation is deemed safe. |languages| is not
+// used any more and will be removed. |format_type| is a bitmask
 // of FormatUrlTypes, see it for details. |unescape_rules| defines how to clean
 // the URL for human readability. You will generally want |UnescapeRule::SPACES|
 // for display to the user if you can handle spaces, or |UnescapeRule::NORMAL|
@@ -128,7 +129,8 @@ inline base::string16 FormatUrl(const GURL& url, const std::string& languages) {
 bool CanStripTrailingSlash(const GURL& url);
 
 // Formats the host in |url| and appends it to |output|.  The host formatter
-// takes the same accept languages component as ElideURL().
+// takes the same accept languages component as ElideURL(), but it does not
+// affect the result. It'll be removed.
 void AppendFormattedHost(const GURL& url,
                          const std::string& languages,
                          base::string16* output);
@@ -139,15 +141,7 @@ void AppendFormattedHost(const GURL& url,
 //
 // The input should be the canonicalized ASCII host name from GURL. This
 // function does NOT accept UTF-8!
-//
-// |languages| is a comma separated list of ISO 639 language codes. It
-// is used to determine whether a hostname is 'comprehensible' to a user
-// who understands languages listed. |host| will be converted to a
-// human-readable form (Unicode) ONLY when each component of |host| is
-// regarded as 'comprehensible'. Scipt-mixing is not allowed except that
-// Latin letters in the ASCII range can be mixed with a limited set of
-// script-language pairs (currently Han, Kana and Hangul for zh,ja and ko).
-// When |languages| is empty, even that mixing is not allowed.
+// |languages| is not used any more and will be removed.
 base::string16 IDNToUnicode(const std::string& host,
                             const std::string& languages);