if (pm.isCanceled()) throw new OperationCanceledException();
	public RefactoringStatus isValid(IProgressMonitor pm) throws CoreException {		RefactoringStatus result= new RefactoringStatus();		pm.beginTask("", fChanges.size()); //$NON-NLS-1$		for (Iterator iter= fChanges.iterator(); iter.hasNext() && !result.hasFatalError();) {			Change change= (Change)iter.next();			if (change.isEnabled())				result.merge(change.isValid(new SubProgressMonitor(pm, 1)));			else				pm.worked(1);		}		pm.done();		return result;	}