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
protected Item getChild(Widget widget, int index) {
		if (widget instanceof TreeItem) {
			return ((TreeItem) widget).getItem(index);
		}
		if (widget instanceof Tree) {
			return ((Tree) widget).getItem(index);
		}
		return null;
	}
	protected void assertContentProviderType(IContentProvider provider) {
		if (provider instanceof ILazyTreeContentProvider) {
			return;
		}
		super.assertContentProviderType(provider);
	}
	protected Object[] getRawChildren(Object parent) {
		if (getContentProvider() instanceof ILazyTreeContentProvider) {
			return new Object[0];
		}
		return super.getRawChildren(parent);
	}
	/**
	 * For a TreeViewer with a tree with the VIRTUAL style bit set, set the
	 * number of children of the given element. To set the number of children of
	 * the invisible root of the tree, the input object is passed as the
	 * element.
	 * 
	 * @param element
	 * @param count
	 *