--- a/dom/encoding/TextDecoder.cpp
+++ b/dom/encoding/TextDecoder.cpp
@@ -26,21 +26,20 @@ TextDecoder::Init(const nsAString& aEnco
   if (label.LowerCaseEqualsLiteral("utf-16")) {
     mUseBOM = true;
     mIsUTF16Family = true;
     mEncoding = "utf-16le";
     // If BOM is used, we can't determine the converter yet.
     return;
   }
 
-  // Run the steps to get an encoding from Encoding.
+  // Let encoding be the result of getting an encoding from label.
+  // If encoding is failure, throw a TypeError.
   if (!EncodingUtils::FindEncodingForLabel(label, mEncoding)) {
-    // If the steps result in failure,
-    // throw a "EncodingError" exception and terminate these steps.
-    aRv.Throw(NS_ERROR_DOM_ENCODING_NOT_SUPPORTED_ERR);
+    aRv.ThrowTypeError(MSG_ENCODING_NOT_SUPPORTED, &label);
     return;
   }
 
   mIsUTF16Family = !strcmp(mEncoding, "utf-16le") ||
                    !strcmp(mEncoding, "utf-16be");
 
   // If the constructor is called with an options argument,
   // and the fatal property of the dictionary is set,

--- a/dom/encoding/TextEncoder.cpp
+++ b/dom/encoding/TextEncoder.cpp
@@ -13,31 +13,28 @@ namespace dom {
 
 void
 TextEncoder::Init(const nsAString& aEncoding,
                   ErrorResult& aRv)
 {
   nsAutoString label(aEncoding);
   EncodingUtils::TrimSpaceCharacters(label);
 
-  // Run the steps to get an encoding from Encoding.
+  // Let encoding be the result of getting an encoding from label.
+  // If encoding is failure, or is none of utf-8, utf-16, and utf-16be,
+  // throw a TypeError.
   if (!EncodingUtils::FindEncodingForLabel(label, mEncoding)) {
-    // If the steps result in failure,
-    // throw an "EncodingError" exception and terminate these steps.
-    aRv.Throw(NS_ERROR_DOM_ENCODING_NOT_SUPPORTED_ERR);
+    aRv.ThrowTypeError(MSG_ENCODING_NOT_SUPPORTED, &label);
     return;
   }
 
-  // Otherwise, if the Name of the returned encoding is not one of
-  // "utf-8", "utf-16", or "utf-16be" throw an "EncodingError" exception
-  // and terminate these steps.
   if (PL_strcasecmp(mEncoding, "utf-8") &&
       PL_strcasecmp(mEncoding, "utf-16le") &&
       PL_strcasecmp(mEncoding, "utf-16be")) {
-    aRv.Throw(NS_ERROR_DOM_ENCODING_NOT_UTF_ERR);
+    aRv.ThrowTypeError(MSG_DOM_ENCODING_NOT_UTF);
     return;
   }
 
   // Create an encoder object for mEncoding.
   nsCOMPtr<nsICharsetConverterManager> ccm =
     do_GetService(NS_CHARSETCONVERTERMANAGER_CONTRACTID);
   if (!ccm) {
     aRv.Throw(NS_ERROR_UNEXPECTED);

--- a/dom/encoding/test/test_BOMEncoding.js
+++ b/dom/encoding/test/test_BOMEncoding.js
@@ -41,17 +41,17 @@ function testBOMEncodingUTF8() {
   // test valid encoding provided with invalid byte OM also provided.
   data = [0xFF, 0xFE, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27];
   expectedString = "\ufffd\ufffd !\"#$%&'";
   testBOMCharset({encoding: "utf-8", data: data, expected: expectedString,
                   msg: "valid utf-8 encoding provided with invalid utf-8 BOM test."});
 
   // test empty encoding provided with invalid byte OM also provided.
   data = [0xFF, 0xFE, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27];
-  testBOMCharset({encoding: "", data: data, error: "EncodingError",
+  testBOMCharset({encoding: "", data: data, error: "TypeError",
                   msg: "empty encoding provided with invalid utf-8 BOM test."});
 }
 
 function testMoreBOMEncoding() {
   var expectedString = "\"\u0412\u0441\u0435 \u0441\u0447\u0430\u0441\u0442\u043B\u0438\u0432\u044B\u0435 \u0441\u0435\u043C\u044C\u0438 \u043F\u043E\u0445\u043E\u0436\u0438 \u0434\u0440\u0443\u0433 \u043D\u0430 \u0434\u0440\u0443\u0433\u0430, \u043A\u0430\u0436\u0434\u0430\u044F \u043D\u0435\u0441\u0447\u0430\u0441\u0442\u043B\u0438\u0432\u0430\u044F \u0441\u0435\u043C\u044C\u044F \u043D\u0435\u0441\u0447\u0430\u0441\u0442\u043B\u0438\u0432\u0430 \u043F\u043E-\u0441\u0432\u043E\u0435\u043C\u0443.\"";
 
  // Testing user provided encoding is UTF-16BE & bom encoding is utf-16le
   var data = [0xFF, 0xFE, 0x00, 0x22, 0x04, 0x12, 0x04, 0x41, 0x04, 0x35, 0x00, 0x20, 0x04, 0x41, 0x04, 0x47, 0x04, 0x30, 0x04, 0x41, 0x04, 0x42, 0x04, 0x3B, 0x04, 0x38, 0x04, 0x32, 0x04, 0x4B, 0x04, 0x35, 0x00, 0x20, 0x04, 0x41, 0x04, 0x35, 0x04, 0x3C, 0x04, 0x4C, 0x04, 0x38, 0x00, 0x20, 0x04, 0x3F, 0x04, 0x3E, 0x04, 0x45, 0x04, 0x3E, 0x04, 0x36, 0x04, 0x38, 0x00, 0x20, 0x04, 0x34, 0x04, 0x40, 0x04, 0x43, 0x04, 0x33, 0x00, 0x20, 0x04, 0x3D, 0x04, 0x30, 0x00, 0x20, 0x04, 0x34, 0x04, 0x40, 0x04, 0x43, 0x04, 0x33, 0x04, 0x30, 0x00, 0x2C, 0x00, 0x20, 0x04, 0x3A, 0x04, 0x30, 0x04, 0x36, 0x04, 0x34, 0x04, 0x30, 0x04, 0x4F, 0x00, 0x20, 0x04, 0x3D, 0x04, 0x35, 0x04, 0x41, 0x04, 0x47, 0x04, 0x30, 0x04, 0x41, 0x04, 0x42, 0x04, 0x3B, 0x04, 0x38, 0x04, 0x32, 0x04, 0x30, 0x04, 0x4F, 0x00, 0x20, 0x04, 0x41, 0x04, 0x35, 0x04, 0x3C, 0x04, 0x4C, 0x04, 0x4F, 0x00, 0x20, 0x04, 0x3D, 0x04, 0x35, 0x04, 0x41, 0x04, 0x47, 0x04, 0x30, 0x04, 0x41, 0x04, 0x42, 0x04, 0x3B, 0x04, 0x38, 0x04, 0x32, 0x04, 0x30, 0x00, 0x20, 0x04, 0x3F, 0x04, 0x3E, 0x00, 0x2D, 0x04, 0x41, 0x04, 0x32, 0x04, 0x3E, 0x04, 0x35, 0x04, 0x3C, 0x04, 0x43, 0x00, 0x2E, 0x00, 0x22];

--- a/dom/encoding/test/test_TextDecoder.js
+++ b/dom/encoding/test/test_TextDecoder.js
@@ -67,29 +67,29 @@ function testConstructorFatalOption(data
 
 function testConstructorEncodingOption(aData, aExpectedString)
 {
   // valid encoding passed
   testCharset({encoding: "iso-8859-11", input: aData, expected: aExpectedString,
     msg: "decoder testing constructor valid encoding."});
 
   // invalid encoding passed
-  testCharset({encoding: "asdfasdf", input: aData, error: "EncodingError",
+  testCharset({encoding: "asdfasdf", input: aData, error: "TypeError",
     msg: "constructor encoding, invalid encoding test."});
 
   // passing spaces for encoding
-  testCharset({encoding: "   ", input: aData, error: "EncodingError",
+  testCharset({encoding: "   ", input: aData, error: "TypeError",
     msg: "constructor encoding, spaces encoding test."});
 
   // passing null for encoding
-  testCharset({encoding: null, input: aData, error: "EncodingError",
+  testCharset({encoding: null, input: aData, error: "TypeError",
     msg: "constructor encoding, \"null\" encoding test."});
 
   // empty encoding passed
-  testCharset({encoding: "", input: aData, error: "EncodingError",
+  testCharset({encoding: "", input: aData, error: "TypeError",
     msg: "constuctor encoding, empty encoding test."});
 
   // replacement character test
   aExpectedString = "\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd"
                   + "\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd"
                   + "\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd"
                   + "\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd"
                   + "\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd"
@@ -332,17 +332,17 @@ function testDecoderGetEncoding()
     {encoding: "euc-jp", labels: ["cseucpkdfmtjapanese", "euc-jp", "x-euc-jp"]},
     {encoding: "iso-2022-jp", labels: ["csiso2022jp", "iso-2022-jp"]},
     {encoding: "shift_jis", labels: ["csshiftjis", "ms_kanji", "shift-jis", "shift_jis", "sjis", "windows-31j", "x-sjis"]},
     {encoding: "euc-kr", labels: ["cseuckr", "csksc56011987", "euc-kr", "iso-ir-149", "korean", "ks_c_5601-1987", "ks_c_5601-1989", "ksc5601", "ksc_5601", "windows-949"]},
     {encoding: "iso-2022-kr", labels: ["csiso2022kr", "iso-2022-kr"]},
     {encoding: "utf-16", labels: ["utf-16", "utf-16le"]},
     {encoding: "utf-16be", labels: ["utf-16be"]},
     {encoding: "x-user-defined", labels: ["x-user-defined"]},
-    {error: "EncodingError", labels: ["x-windows-949", "\u0130SO-8859-1"]},
+    {error: "TypeError", labels: ["x-windows-949", "\u0130SO-8859-1"]},
   ];
 
   for (var le of labelEncodings) {
     for (var label of le.labels) {
       try {
         var decoder = TextDecoder(label);
       } catch (e) {
         assert_true(!!le.error, label + " shoud not throw " + e.name);

--- a/dom/encoding/test/test_TextEncoder.js
+++ b/dom/encoding/test/test_TextEncoder.js
@@ -90,36 +90,36 @@ function testEncodeUTF16ToUTF16()
 
 function testConstructorEncodingOption(aData, aExpectedString)
 {
   // valid encoding passed
   testSingleString({encoding: "UTF-8", input: aData, expected: aExpectedString,
     msg: "testing encoding with valid utf-8 encoding."});
 
   // passing spaces for encoding
-  testSingleString({encoding: "   ", input: aData, error: "EncodingError",
+  testSingleString({encoding: "   ", input: aData, error: "TypeError",
     msg: "constructor encoding, spaces encoding test."});
 
   // invalid encoding passed
-  testSingleString({encoding: "asdfasdf", input: aData, error: "EncodingError",
+  testSingleString({encoding: "asdfasdf", input: aData, error: "TypeError",
     msg: "constructor encoding, invalid encoding test."});
 
   // null encoding passed
-  testSingleString({encoding: null, input: aData, error: "EncodingError",
+  testSingleString({encoding: null, input: aData, error: "TypeError",
     msg: "constructor encoding, \"null\" encoding test."});
 
   // null encoding passed
-  testSingleString({encoding: "", input: aData, error: "EncodingError",
+  testSingleString({encoding: "", input: aData, error: "TypeError",
     msg: "constructor encoding, empty encoding test."});
 }
 
 function testEncodingValues(aData, aExpectedString)
 {
   var encoding = "ISO-8859-11";
-  testSingleString({encoding: aData, input: encoding, error: "EncodingError",
+  testSingleString({encoding: aData, input: encoding, error: "TypeError",
     msg: "encoder encoding values test."});
 }
 
 function testInputString(aData, aExpectedString)
 {
   //Test null input string
   testSingleString({encoding: "utf-8", input: "", expected: [],
     msg: "encoder null input string test."});