Bug 105697 [Undo] - OperationHistoryEvent - cannot distinguish between canceled event or failed event
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/DefaultOperationHistory.java
import org.eclipse.core.runtime.Status;
/**
 * <p>
 * A base implementation of IOperationHistory that implements a linear undo and
 * redo model . The most recently added operation is available for undo, and the
 * most recently undone operation is available for redo.
 * </p>
 * <p>
 * If the operation eligible for undo is not in a state where it can be undone,
 * then no undo is available. No other operations are considered. Likewise, if
 * the operation available for redo cannot be redone, then no redo is available.
 * </p>
 * <p>
 * Implementations for the direct undo and redo of a specified operation are
 * available. If a strict linear undo is to be enforced, than an
 * IOperationApprover should be installed that prevents undo and redo of any
 * operation that is not the most recently undone or redone operation in all of
 * its undo contexts.
 * </p>
 * <p>
 * The data structures used by the DefaultOperationHistory are synchronized, and
 * entry points that modify the undo and redo history concurrently are also
 * synchronized. This means that the DefaultOperationHistory is relatively
 * "thread-friendly" in its implementation.  Outbound notifications or operation
 * approval requests will occur on the thread that initiated the request.
 * Clients may use DefaultOperationHistory API from any thread; however,
 * listeners or operation approvers that receive notifications from the
 * DefaultOperationHistory must be prepared to receive these notifications from
 * a background thread. Any UI access occurring inside these notifications must
 * be properly synchronized using the techniques specified by the client's