Bug 93360 [Viewers] getChild still used in indexForElement
indexForElement() in AbstractTreeViewer still uses getChild() and not getChildren(). This should probably also change to using getChildren() and do the same thing as insertionPosition().
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
list.add(e);
        }
        return list;
    }
    /**
     * Handles a tree collapse event from the SWT widget.
     * 
     * @param event
     *           the SWT tree event
     */
    protected void handleTreeCollapse(TreeEvent event) {
        if (event.item.getData() != null) {
            fireTreeCollapsed(new TreeExpansionEvent(this, event.item.getData()));
        }
    }
    /**
     * Handles a tree expand event from the SWT widget.
     * 
     * @param event
     *           the SWT tree event
     */
    protected void handleTreeExpand(TreeEvent event) {
        createChildren(event.item);
        if (event.item.getData() != null) {
            fireTreeExpanded(new TreeExpansionEvent(this, event.item.getData()));
        }
    }
    
    protected void hookControl(Control control) {
        super.hookControl(control);