diff -r 000000000000 -r 6474c204b198 dom/encoding/EncodingUtils.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/encoding/EncodingUtils.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,73 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/EncodingUtils.h"
+
+#include "mozilla/ArrayUtils.h" // ArrayLength
+#include "nsUConvPropertySearch.h"
+#include "nsIUnicodeDecoder.h"
+#include "nsIUnicodeEncoder.h"
+#include "nsComponentManagerUtils.h"
+
+namespace mozilla {
+namespace dom {
+
+static const char* labelsEncodings[][3] = {
+#include "labelsencodings.properties.h"
+};
+
+bool
+EncodingUtils::FindEncodingForLabel(const nsACString& aLabel,
+                                    nsACString& aOutEncoding)
+{
+  // Save aLabel first because it may refer the same string as aOutEncoding.
+  nsCString label(aLabel);
+
+  EncodingUtils::TrimSpaceCharacters(label);
+  if (label.IsEmpty()) {
+    aOutEncoding.Truncate();
+    return false;
+  }
+
+  ToLowerCase(label);
+  return NS_SUCCEEDED(nsUConvPropertySearch::SearchPropertyValue(
+      labelsEncodings, ArrayLength(labelsEncodings), label, aOutEncoding));
+}
+
+bool
+EncodingUtils::IsAsciiCompatible(const nsACString& aPreferredName)
+{
+  return !(aPreferredName.LowerCaseEqualsLiteral("utf-16") ||
+           aPreferredName.LowerCaseEqualsLiteral("utf-16be") ||
+           aPreferredName.LowerCaseEqualsLiteral("utf-16le") ||
+           aPreferredName.LowerCaseEqualsLiteral("replacement") ||
+           aPreferredName.LowerCaseEqualsLiteral("hz-gb-2312") ||
+           aPreferredName.LowerCaseEqualsLiteral("utf-7") ||
+           aPreferredName.LowerCaseEqualsLiteral("x-imap4-modified-utf7"));
+}
+
+already_AddRefed<nsIUnicodeDecoder>
+EncodingUtils::DecoderForEncoding(const nsACString& aEncoding)
+{
+  nsAutoCString contractId(NS_UNICODEDECODER_CONTRACTID_BASE);
+  contractId.Append(aEncoding);
+
+  nsCOMPtr<nsIUnicodeDecoder> decoder = do_CreateInstance(contractId.get());
+  MOZ_ASSERT(decoder, "Tried to create decoder for unknown encoding.");
+  return decoder.forget();
+}
+
+already_AddRefed<nsIUnicodeEncoder>
+EncodingUtils::EncoderForEncoding(const nsACString& aEncoding)
+{
+  nsAutoCString contractId(NS_UNICODEENCODER_CONTRACTID_BASE);
+  contractId.Append(aEncoding);
+
+  nsCOMPtr<nsIUnicodeEncoder> encoder = do_CreateInstance(contractId.get());
+  MOZ_ASSERT(encoder, "Tried to create encoder for unknown encoding.");
+  return encoder.forget();
+}
+
+} // namespace dom
+} // namespace mozilla