diff -r 000000000000 -r 6474c204b198 intl/uconv/src/nsReplacementToUnicode.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/intl/uconv/src/nsReplacementToUnicode.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,56 @@
+/* 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 "nsReplacementToUnicode.h"
+
+nsReplacementToUnicode::nsReplacementToUnicode()
+ : mSeenByte(false)
+{
+}
+
+NS_IMETHODIMP
+nsReplacementToUnicode::Convert(const char* aSrc,
+                                int32_t* aSrcLength,
+                                char16_t* aDest,
+                                int32_t* aDestLength)
+{
+  if (mSeenByte || !(*aSrcLength)) {
+    *aDestLength = 0;
+    return NS_PARTIAL_MORE_INPUT;
+  }
+  if (mErrBehavior == kOnError_Signal) {
+    mSeenByte = true;
+    *aSrcLength = 0;
+    *aDestLength = 0;
+    return NS_ERROR_ILLEGAL_INPUT;
+  }
+  if (!(*aDestLength)) {
+    *aSrcLength = -1;
+    return NS_PARTIAL_MORE_OUTPUT;
+  }
+  mSeenByte = true;
+  *aDest = 0xFFFD;
+  *aDestLength = 1;
+  return NS_PARTIAL_MORE_INPUT;
+}
+
+NS_IMETHODIMP
+nsReplacementToUnicode::GetMaxLength(const char* aSrc,
+                          int32_t aSrcLength,
+                          int32_t* aDestLength)
+{
+  if (!mSeenByte && aSrcLength > 0) {
+    *aDestLength = 1;
+  } else {
+    *aDestLength = 0;
+  }
+  return NS_EXACT_LENGTH;
+}
+
+NS_IMETHODIMP
+nsReplacementToUnicode::Reset()
+{
+  mSeenByte = false;
+  return NS_OK;
+}