Bug 88352 Operation supports leaks contexts via action handler
I20050315-1100 Susan, this is a different leak from the one that I reported. Test Case: 1. open text editor 2. close text editor ==> DefaultUndoManager is leaked due to undo/redo actions handlers still holding on to the context.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/IUndoableOperation.java
* @return <code>true</code> if the context is present, <code>false</code>
	 *         if it is not.
	 */
	boolean hasContext(IUndoContext context);
	/**
	 * Redo the operation. This method should only be called after an operation
	 * has been undone.
	 * 
	 * @param monitor -
	 *            the progress monitor (or <code>null</code>) to use for
	 *            reporting progress to the user.
	 * @param info -
	 *            the IAdaptable (or <code>null</code>) provided by the
	 *            caller containing additional information. When this API is
	 *            called from the UI, callers can use this to provide additional
	 *            info for prompting the user. If an IAdaptable is provided,
	 *            callers are encourated to provide an adapter for the
	 *            org.eclipse.swt.widgets.Shell.class.
	 * @return the IStatus of the redo. The status severity should be set to
	 *         <code>OK</code> if the redo was successful, and
	 *         <code>ERROR</code> if it was not. Any other status is assumed
	 *         to represent an incompletion of the redo.
	 * @throws ExecutionException
	 *             if an exception occurred during redo.
	 */
	IStatus redo(IProgressMonitor monitor, IAdaptable info)
			throws ExecutionException;
	/**
	 * Remove the specified context from the operation. This method has no
	 * effect if the context is not present.