Implement "replacement" text encoding.

Source/modules/encoding/TextDecoder.cpp

Index: Source/modules/encoding/TextDecoder.cpp
diff --git a/Source/modules/encoding/TextDecoder.cpp b/Source/modules/encoding/TextDecoder.cpp
index 541540e6674acd489317f1660689209f67eec0a7..15dc9a9f1c9b33079a11ca9bc1393e143f00fe0d 100644
--- a/Source/modules/encoding/TextDecoder.cpp
+++ b/Source/modules/encoding/TextDecoder.cpp
@@ -43,7 +43,7 @@ PassRefPtrWillBeRawPtr<TextDecoder> TextDecoder::create(const String& label, con
     const String& encodingLabel = label.isNull() ? String("utf-8") : label;
 
     WTF::TextEncoding encoding(encodingLabel);
-    if (!encoding.isValid()) {
+    if (!encoding.isValid() || !strcmp(encoding.name(), "replacement")) {
         exceptionState.throwTypeError("The encoding label provided ('" + encodingLabel + "') is invalid.");
         return nullptr;
     }
@@ -51,13 +51,12 @@ PassRefPtrWillBeRawPtr<TextDecoder> TextDecoder::create(const String& label, con
     bool fatal = false;
     options.get("fatal", fatal);
 
-    return adoptRefWillBeNoop(new TextDecoder(encoding.name(), fatal));
+    return adoptRefWillBeNoop(new TextDecoder(encodingLabel, encoding.name(), fatal));
 }
 
-
-TextDecoder::TextDecoder(const String& encoding, bool fatal)
-    : m_encoding(encoding)
-    , m_codec(newTextCodec(m_encoding))
+TextDecoder::TextDecoder(const String& label, const String& name, bool fatal)
+    : m_encoding(name)
+    , m_codec(newTextCodec(label))
     , m_fatal(fatal)
     , m_bomSeen(false)
 {
@@ -69,7 +68,7 @@ TextDecoder::~TextDecoder()
 
 String TextDecoder::encoding() const
 {
-    String name = String(m_encoding.name()).lower();
+    String name = m_encoding.lower();
     // Where possible, encoding aliases should be handled by changes to Chromium's ICU or Blink's WTF.
     // The same codec is used, but WTF maintains a different name/identity for these.
     if (name == "iso-8859-1" || name == "us-ascii")
@@ -97,8 +96,7 @@ String TextDecoder::decode(ArrayBufferView* input, const Dictionary& options, Ex
 
     if (!m_bomSeen && !s.isEmpty()) {
         m_bomSeen = true;
-        String name(m_encoding.name());
-        if ((name == "UTF-8" || name == "UTF-16LE" || name == "UTF-16BE") && s[0] == 0xFEFF)
+        if ((m_encoding == "UTF-8" || m_encoding == "UTF-16LE" || m_encoding == "UTF-16BE") && s[0] == 0xFEFF)
             s.remove(0);
     }