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
/**
	 * Singleton instance.
	 */
	private static WorkspaceUndoMonitor instance;
	/**
	 * Number of workspace changes that will cause validation of undo history
	 */
	private static int CHANGE_THRESHHOLD = 10;
	
	/**
	 * Prefix to use on debug info
	 */
	private static String DEBUG_PREFIX = "Workspace Undo Monitor:  "; 
	/**
	 * Get the singleton instance of this class.
	 * 
	 * @return the singleton instance of this class.
	 */
	public static WorkspaceUndoMonitor getInstance() {
		if (instance == null) {
			instance = new WorkspaceUndoMonitor();
		}
		return instance;
	}
	/**
	 * Number of workspace changes that have occurred since the last undoable
	 * operation was executed, undone, or redone.
	 */