Avoid using language hint in encoding detection

third_party/WebKit/Source/platform/text/TextEncodingDetector.cpp

 /*
  * Copyright (C) 2008, 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 25 matching lines @@
 
 namespace blink {
 
 bool detectTextEncoding(const char* data,
                         size_t length,
                         const char* hintEncodingName,
                         const KURL& hintUrl,
                         const char* hintUserLanguage,
                         WTF::TextEncoding* detectedEncoding) {
   *detectedEncoding = WTF::TextEncoding();
-  Language language;
-  LanguageFromCode(hintUserLanguage, &language);
+  // In general, do not use language hint. This helps get more
+  // deterministic encoding detection results across devices. Note that local
+  // file resources can still benefit from the hint.
+  Language language = UNKNOWN_LANGUAGE;
+  if (hintUrl.protocol() == "file")
+    LanguageFromCode(hintUserLanguage, &language);
   int consumedBytes;
   bool isReliable;
   Encoding encoding = CompactEncDet::DetectEncoding(
       data, length, hintUrl.getString().ascii().data(), nullptr, nullptr,
       EncodingNameAliasToEncoding(hintEncodingName), language,
       CompactEncDet::WEB_CORPUS,
       false,  // Include 7-bit encodings to detect ISO-2022-JP
       &consumedBytes, &isReliable);
 
   // Should return false if the detected encoding is UTF8. This helps prevent
   // modern web sites from neglecting proper encoding labelling and simply
   // relying on browser-side encoding detection. Encoding detection is supposed
   // to work for web sites with legacy encoding only (so this doesn't have to
   // be applied to local file resources).
   // Detection failure leads |TextResourceDecoder| to use its default encoding
   // determined from system locale or TLD.
   if (encoding == UNKNOWN_ENCODING ||
       (hintUrl.protocol() != "file" && encoding == UTF8))
     return false;
 
   *detectedEncoding = WTF::TextEncoding(MimeEncodingName(encoding));
   return true;
 }
 
 }  // namespace blink