diff -r 000000000000 -r 6474c204b198 xpcom/string/src/nsTString.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/string/src/nsTString.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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/. */
+
+nsTAdoptingString_CharT&
+nsTAdoptingString_CharT::operator=( const self_type& str )
+  {
+    // This'll violate the constness of this argument, that's just
+    // the nature of this class...
+    self_type* mutable_str = const_cast<self_type*>(&str);
+
+    if (str.mFlags & F_OWNED)
+      {
+        // We want to do what Adopt() does, but without actually incrementing
+        // the Adopt count.  Note that we can be a little more straightforward
+        // about this than Adopt() is, because we know that str.mData is
+        // non-null.  Should we be able to assert that str is not void here?
+        NS_ASSERTION(str.mData, "String with null mData?");
+        Finalize();
+        mData = str.mData;
+        mLength = str.mLength;
+        SetDataFlags(F_TERMINATED | F_OWNED);
+
+        // Make str forget the buffer we just took ownership of.
+        new (mutable_str) self_type();
+      }
+    else
+      {
+        Assign(str);
+
+        mutable_str->Truncate();
+      }
+
+    return *this;
+  }
+
+void
+nsTString_CharT::Rebind( const char_type* data, size_type length )
+  {
+    // If we currently own a buffer, release it.
+    Finalize();
+
+    mData = const_cast<char_type*>(data);
+    mLength = length;
+    SetDataFlags(F_TERMINATED);
+    AssertValidDepedentString();
+  }
+