diff -r 000000000000 -r 6474c204b198 dom/plugins/ipc/ScopedMethodFactory.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/plugins/ipc/ScopedMethodFactory.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,87 @@
+/* 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/. */
+
+#ifndef mozilla_plugins_ScopedMethodFactory_h
+#define mozilla_plugins_ScopedMethodFactory_h
+
+#include <base/task.h>
+
+/*
+ * This is based on the ScopedRunnableMethodFactory from ipc/chromium/src/base/task.h
+ * Chromiums factories assert if tasks are created and run on different threads,
+ * which is something we need to do in PluginModuleParent (hang UI vs. main thread).
+ * ScopedMethodFactory just provides cancellable tasks that don't assert this.
+ */
+
+namespace mozilla {
+namespace plugins {
+
+template<class T>
+class ScopedMethodFactory : public RevocableStore
+{
+private:
+  template<class TaskType>
+  class TaskWrapper : public TaskType
+  {
+  public:
+    explicit TaskWrapper(RevocableStore* store) : revocable_(store) { }
+
+    virtual void Run() {
+      if (!revocable_.revoked())
+        TaskType::Run();
+    }
+
+  private:
+    Revocable revocable_;
+  };
+
+public:
+  explicit ScopedMethodFactory(T* object) : object_(object) { }
+
+  template <class Method>
+  inline Task* NewRunnableMethod(Method method) {
+    typedef TaskWrapper<RunnableMethod<Method, Tuple0> > TaskWrapper;
+
+    TaskWrapper* task = new TaskWrapper(this);
+    task->Init(object_, method, MakeTuple());
+    return task;
+  }
+
+  template <class Method, class A>
+  inline Task* NewRunnableMethod(Method method, const A& a) {
+    typedef TaskWrapper<RunnableMethod<Method, Tuple1<A> > > TaskWrapper;
+
+    TaskWrapper* task = new TaskWrapper(this);
+    task->Init(object_, method, MakeTuple(a));
+    return task;
+  }
+
+protected:
+  template <class Method, class Params>
+  class RunnableMethod : public Task {
+   public:
+    RunnableMethod() { }
+
+    void Init(T* obj, Method meth, const Params& params) {
+      obj_ = obj;
+      meth_ = meth;
+      params_ = params;
+    }
+
+    virtual void Run() { DispatchToMethod(obj_, meth_, params_); }
+
+   private:
+    T* obj_;
+    Method meth_;
+    Params params_;
+  };
+
+private:
+  T* object_;
+};
+
+} // namespace plugins
+} // namespace mozilla
+
+#endif // mozilla_plugins_ScopedMethodFactory_h