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
/**
     * Expands the root of the viewer's tree to the given level.
     * 
     * @param level
     *           non-negative level, or <code>ALL_LEVELS</code> to expand all
     *           levels of the tree
     */
    public void expandToLevel(int level) {
        expandToLevel(getRoot(), level);
    }
    /**
     * Expands all ancestors of the given element so that the given element
     * becomes visible in this viewer's tree control, and then expands the
     * subtree rooted at the given element to the given level.
     * 
     * @param element
     *           the element
     * @param level
     *           non-negative level, or <code>ALL_LEVELS</code> to expand all
     *           levels of the tree
     */
    public void expandToLevel(Object element, int level) {
        Widget w = internalExpand(element, true);
        if (w != null)
            internalExpandToLevel(w, level);
    }
    /**
     * Fires a tree collapsed event. Only listeners registered at the time this
     * method is called are notified.
     *