  *  The ViewTransitionBase class is the base class for all view transitions.  
  *  It is not intended to be used as a transition on its own.
  *  In addition to providing common convenience and helper methods used by 
- *  view transitions this class also provides a default action bar transition 
+ *  view transitions, this class provides a default action bar transition 
  *  sequence.
  * 
  *  <p>When a view transition is initialized, the owning view navigator 

     *  Called by the default <code>prepareForPlay()</code> implementation, 
     *  this method is responsible for creating the Spark effect 
     *  played on the action bar when the transition starts.  
     *  This method should be overridden by sub classes if a custom action bar 
     *  effect is required.  
     *  By default, this method returns a basic action bar effect.
     * 

[Event(name="transitionStart", type="mx.events.FlexEvent")]

/**
 *  Dispatched when the transition completes.
 * 
 *  @eventType mx.events.FlexEvent.TRANSITION_START
 *  
 *  @langversion 3.0
 *  @playerversion AIR 2.5
