diff -r 000000000000 -r 6474c204b198 toolkit/mozapps/extensions/test/xpcshell/test_XPIcancel.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_XPIcancel.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,66 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+// Test the cancellable doing/done/cancelAll API in XPIProvider
+
+let scope = Components.utils.import("resource://gre/modules/addons/XPIProvider.jsm");
+let XPIProvider = scope.XPIProvider;
+
+function run_test() {
+  // Check that cancelling with nothing in progress doesn't blow up
+  XPIProvider.cancelAll();
+
+  // Check that a basic object gets cancelled
+  let getsCancelled = {
+    isCancelled: false,
+    cancel: function () {
+      if (this.isCancelled)
+        do_throw("Already cancelled");
+      this.isCancelled = true;
+    }
+  };
+  XPIProvider.doing(getsCancelled);
+  XPIProvider.cancelAll();
+  do_check_true(getsCancelled.isCancelled);
+
+  // Check that if we complete a cancellable, it doesn't get cancelled
+  let doesntGetCancelled = {
+    cancel: () => do_throw("This should not have been cancelled")
+  };
+  XPIProvider.doing(doesntGetCancelled);
+  do_check_true(XPIProvider.done(doesntGetCancelled));
+  XPIProvider.cancelAll();
+
+  // A cancellable that adds a cancellable
+  getsCancelled.isCancelled = false;
+  let addsAnother = {
+    isCancelled: false,
+    cancel: function () {
+      if (this.isCancelled)
+        do_throw("Already cancelled");
+      this.isCancelled = true;
+      XPIProvider.doing(getsCancelled);
+    }
+  }
+  XPIProvider.doing(addsAnother);
+  XPIProvider.cancelAll();
+  do_check_true(addsAnother.isCancelled);
+  do_check_true(getsCancelled.isCancelled);
+
+  // A cancellable that removes another. This assumes that Set() iterates in the
+  // order that members were added
+  let removesAnother = {
+    isCancelled: false,
+    cancel: function () {
+      if (this.isCancelled)
+        do_throw("Already cancelled");
+      this.isCancelled = true;
+      XPIProvider.done(doesntGetCancelled);
+    }
+  }
+  XPIProvider.doing(removesAnother);
+  XPIProvider.doing(doesntGetCancelled);
+  XPIProvider.cancelAll();
+  do_check_true(removesAnother.isCancelled);
+}