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
protected abstract void doExecute(IProgressMonitor monitor,
			IAdaptable uiInfo) throws CoreException;
	/**
	 * Return whether the proposed operation is valid. The default
	 * implementation simply checks to see if the flag has been marked as
	 * invalid, relying on subclasses to mark the flag invalid when appropriate.
	 * 
	 * @return the validity flag
	 */
	protected boolean isValid() {
		return isValid;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.core.commands.operations.IAdvancedUndoableOperation#aboutToNotify(org.eclipse.core.commands.operations.OperationHistoryEvent)
	 */
	public void aboutToNotify(OperationHistoryEvent event) {
		
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.core.commands.operations.IAdvancedUndoableOperation#getAffectedObjects()
	 */
	public Object[] getAffectedObjects() {
		return resources;
	}
	/**
	 * Return a status indicating the projected outcome of executing the