Bug 161738 [Undo] - API - promote ability to quietly compute status to operations API
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/undo/WorkspaceUndoMonitor.java
}
	/**
	 * Shutdown the workspace undo monitor. Unhooks the listeners.
	 */
	public void shutdown() {
		if (Policy.DEBUG_UNDOMONITOR) {
			System.out.println(DEBUG_PREFIX + "Shutting Down"); 
		}
		if (resourceListener != null) {
			ResourcesPlugin.getWorkspace().removeResourceChangeListener(
					resourceListener);
		}
		if (historyListener != null) {
			getOperationHistory().removeOperationHistoryListener(
					historyListener);
		}
	}
	/**
	 * Get the operation history.
	 */
	private IOperationHistory getOperationHistory() {
		return PlatformUI.getWorkbench().getOperationSupport()
				.getOperationHistory();
	}
	/**
	 * Check the pending undoable operation to see if it is still valid.
	 */
	private void checkOperationHistory() {
		if (Policy.DEBUG_UNDOMONITOR) {
			System.out.println(DEBUG_PREFIX + "Checking Operation History...");