Tweaking WebPageSerializerImpl to emit a BOM for UTF16/32.

third_party/WebKit/Source/web/WebPageSerializerImpl.cpp

 /*
  * Copyright (C) 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 435 matching lines @@
 {
     bool didSerialization = false;
 
     Document* document = m_specifiedWebLocalFrameImpl->frame()->document();
     const KURL& url = document->url();
 
     if (url.isValid()) {
         didSerialization = true;
 
         const WTF::TextEncoding& textEncoding = document->encoding().isValid() ? document->encoding() : UTF8Encoding();
+        if (textEncoding.isNonByteBasedEncoding()) {
+            const UChar bomCharacter = 0xFEFF;

[jsbell, 2015/12/08 01:19:07]

nit: maybe call this `byteOrderMark` as it's not technically a character and not
everyone knows BOM

[Łukasz Anforowicz, 2015/12/09 00:50:59]

Done.

+            m_dataBuffer.append(bomCharacter);
+        }
 
         SerializeDomParam param(url, textEncoding, document, m_localDirectoryName);
 
         Element* documentElement = document->documentElement();
         if (documentElement)
             buildContentForNode(documentElement, &param);
 
         encodeAndFlushBuffer(WebPageSerializerClient::CurrentFrameIsFinished, &param, ForceFlush);
     } else {
         // Report empty contents for invalid URLs.
         m_client->didSerializeDataForFrame(
             WebCString(), WebPageSerializerClient::CurrentFrameIsFinished);
     }
 
     ASSERT(m_dataBuffer.isEmpty());
     return didSerialization;
 }
 
 }  // namespace blink