Hierarchy. Hierarchy. Hierarchy!!!

media/base/callback.h

 // Copyright (c) 2010 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.
 
 // Some basic utilities for aiding in the management of Tasks and Callbacks.
 //
 // AutoTaskRunner, and its brother AutoCallbackRunner are the scoped_ptr
 // equivalents for callbacks.  They are useful for ensuring a callback is
 // executed and delete in the face of multiple return points in a function.
 //
 // TaskToCallbackAdapter converts a Task to a Callback0::Type since the two type
-// heirarchies are strangely separate.
+// hierarchies are strangely separate.
 //
 // CleanupCallback wraps another Callback and provides the ability to register
 // objects for deletion as well as cleanup tasks that will be run on the
 // callback's destruction.  The deletion and cleanup tasks will be run on
 // whatever thread the CleanupCallback is destroyed in.
 
 #ifndef MEDIA_BASE_CALLBACK_
 #define MEDIA_BASE_CALLBACK_
 
 #include <vector>
@@ skipping 92 matching lines @@
  private:
   scoped_ptr<CallbackType> callback_;
   std::vector<Task*> run_when_done_;
 
   DISALLOW_COPY_AND_ASSIGN(CleanupCallback);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_CALLBACK_