Bug 154064 Need a way to access the TreeItem or TableItem on a refresh
It is not currently possible to know when an item is refreshed. This is required for ownerDraw support in viewers.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewer.java
private TooltipSupport tooltipSupport;
	/**
	 * Create a new instance of the receiver.
	 */
	public ColumnViewer() {
		super();
		tooltipSupport = new TooltipSupport(this);
	}
	/**
	 * Get the cell at this point.
	 * <p>
	 * <i>Subclasses should overwrite this method and provide a meaningful
	 * implementation</i>