diff -r 000000000000 -r 6474c204b198 mobile/android/base/util/NativeJSContainer.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/util/NativeJSContainer.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,39 @@
+/* -*- Mode: Java; c-basic-offset: 4; tab-width: 4; indent-tabs-mode: nil; -*-
+ * 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/. */
+
+package org.mozilla.gecko.util;
+
+import org.mozilla.gecko.mozglue.JNITarget;
+
+/**
+ * NativeJSContainer is a wrapper around the SpiderMonkey JSAPI to make it possible to
+ * access Javascript objects in Java.
+ *
+ * A container must only be used on the thread it is attached to. To use it on another
+ * thread, call {@link #clone()} to make a copy, and use the copy on the other thread.
+ * When a copy is first used, it becomes attached to the thread using it.
+ */
+@JNITarget
+public final class NativeJSContainer extends NativeJSObject
+{
+    private long mNativeObject;
+
+    private NativeJSContainer(long nativeObject) {
+        mNativeObject = nativeObject;
+    }
+
+    /**
+     * Make a copy of this container for use by another thread. When the copy is first used,
+     * it becomes attached to the thread using it.
+     */
+    @Override
+    public native NativeJSContainer clone();
+
+    /**
+     * Dispose all associated native objects. Subsequent use of any objects derived from
+     * this container will throw a NullPointerException.
+     */
+    public native void dispose();
+}