Bug 161738 [Undo] - API - promote ability to quietly compute status to operations API
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/undo/AbstractWorkspaceOperation.java
*            caller in order to supply UI information for prompting the
	 *            user if necessary. When this parameter is not
	 *            <code>null</code>, it contains an adapter for the
	 *            org.eclipse.swt.widgets.Shell.class
	 * @return the IStatus of the undo. The status severity should be set to
	 *         <code>OK</code> if the operation was successful, and
	 *         <code>ERROR</code> if it was not. Any other status is assumed
	 *         to represent an incompletion of the undo. *
	 * @throws ExecutionException
	 *             if an exception occurred during execution.
	 * @see org.eclipse.core.commands.operations.IUndoableOperation#undo(org.eclipse.core.runtime.IProgressMonitor,
	 *      org.eclipse.core.runtime.IAdaptable)
	 */
	public IStatus undo(IProgressMonitor monitor, final IAdaptable uiInfo)
			throws ExecutionException {
		try {
			getWorkspace().run(new IWorkspaceRunnable() {
				public void run(IProgressMonitor monitor) throws CoreException {
					doUndo(monitor, uiInfo);
				}
			}, getUndoSchedulingRule(), IWorkspace.AVOID_UPDATE, null);
		} catch (final CoreException e) {
			throw new ExecutionException(NLS.bind(
					UndoMessages.AbstractWorkspaceOperation_UndoErrorTitle,
					getLabel()), e);
		}
		isValid = true;
		return Status.OK_STATUS;
	}
	/**