Tweaking WebPageSerializerImpl to emit a BOM for UTF16/32.

third_party/WebKit/Source/wtf/text/TextEncoding.cpp

 /*
  * Copyright (C) 2004, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov <ap@nypop.com>
  * Copyright (C) 2007-2009 Torch Mobile, Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 66 matching lines @@
 
     OwnPtr<TextCodec> textCodec = newTextCodec(*this);
     CString encodedString;
     if (string.is8Bit())
         encodedString = textCodec->encode(string.characters8(), string.length(), handling);
     else
         encodedString = textCodec->encode(string.characters16(), string.length(), handling);
     return encodedString;
 }
 
+CString TextEncoding::encodeBOMifApplicable() const
+{
+    // TODO(lukasza): Store |textCodec| in a member field, so it can be reused
+    // across repeated calls to encode and/or encodeBOMifApplicable.

[jsbell, 2015/12/07 22:53:51]

That would change the behavior for stateful encodings, unfortunately.

Callers can use TextCodec directly if that level of control is desired. (e.g.
Source/modules/TextEncoding.cpp)

+    OwnPtr<TextCodec> textCodec = newTextCodec(*this);
+    if (!textCodec->shouldIncludeBOM())
+        return "";
+
+    const UChar bomCharacter = 0xFEFF;
+    return textCodec->encode(&bomCharacter, 1, QuestionMarksForUnencodables);
+}
+
 bool TextEncoding::usesVisualOrdering() const
 {
     if (noExtendedTextEncodingNameUsed())
         return false;
 
     static const char* const a = atomicCanonicalTextEncodingName("ISO-8859-8");
     return m_name == a;
 }
 
 bool TextEncoding::isNonByteBasedEncoding() const
@@ skipping 79 matching lines @@
     return globalUTF8Encoding;
 }
 
 const TextEncoding& WindowsLatin1Encoding()
 {
     AtomicallyInitializedStaticReference(const TextEncoding, globalWindowsLatin1Encoding, new TextEncoding("WinLatin1"));
     return globalWindowsLatin1Encoding;
 }
 
 } // namespace WTF