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/TreeViewer.java
* <p>
	 * If the label provider is an <code>ILabelProvider</code>, then it
	 * provides only the label text and image for the first column, and any
	 * remaining columns are blank. Implementers of <code>ILabelProvider</code>
	 * may also implement {@link IColorProvider} and/or {@link IFontProvider} to
	 * provide colors and/or fonts.
	 * </p>
	 */
	public void setLabelProvider(IBaseLabelProvider labelProvider) {
		Assert.isTrue(labelProvider instanceof ITableLabelProvider
				|| labelProvider instanceof ILabelProvider);
		clearColumnParts();
		super.setLabelProvider(labelProvider);
		
	}
	/**
	 * Clear the viewer parts for the columns
	 */
	private void clearColumnParts() {
		TreeColumn[] columns = getTree().getColumns();
		if(columns.length == 0)
			getTree().setData(ViewerColumn.COLUMN_VIEWER_KEY,null);
		else{
			for (int i = 0; i < columns.length; i++) {
				columns[i].setData(ViewerColumn.COLUMN_VIEWER_KEY,null);
				
			}
		}
		
	}