Bug 89031 [Undo/Redo] IWorkbench#getOperationSupport() marked experimental
IWorkbench#getOperationSupport() marked experimental
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/OperationHistoryEvent.java
/**
	 * ABOUT_TO_EXECUTE indicates that an operation is about to execute.
	 * Listeners should prepare for the execution as appropriate. Listeners will
	 * receive a done notification if the operation is successful, or an
	 * operationNotCompleted notification if the execution is cancelled or
	 * otherwise fails. This notification is only received for those operations
	 * executed by the operation history. Operations that are added to the
	 * history after execution do not trigger these notifications.