Move media library AutoTaskRunner to base and rename ScopedTaskRunner.

base/task.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_TASK_H_
 #define BASE_TASK_H_
 #pragma once
 
 #include "base/base_api.h"
 #include "base/debug/alias.h"
@@ skipping 528 matching lines @@
 
 template <class Function, class A, class B, class C, class D, class E,
           class F, class G, class H>
 inline Task* NewRunnableFunction(Function function, const A& a, const B& b,
                                  const C& c, const D& d, const E& e, const F& f,
                                  const G& g, const H& h) {
   return new RunnableFunction<Function, Tuple8<A, B, C, D, E, F, G, H> >(
       function, MakeTuple(a, b, c, d, e, f, g, h));
 }
 
+namespace base {
+
+// ScopedTaskRunner is akin to scoped_ptr for Tasks.  It ensures that the Task
+// is executed and deleted no matter how the current scope exits.
+class BASE_API ScopedTaskRunner {
+ public:
+  // Takes ownership of the task.
+  explicit ScopedTaskRunner(Task* task);
+  ~ScopedTaskRunner();
+
+  Task* Release();
+
+ private:
+  Task* task_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(ScopedTaskRunner);
+};
+
+}  // namespace base
+
 #endif  // BASE_TASK_H_