Bug 72615 [Viewers] Need and ITableFontProvider
We released an ITabelColorProvider for M2 - we should have a corresponding ITableFontProvider
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
protected abstract Item[] getChildren(Widget widget);
    /**
     * Returns whether the given SWT item is expanded or collapsed.
     * 
     * @param item
     *           the item
     * @return <code>true</code> if the item is considered expanded and
     *         <code>false</code> if collapsed
     */
    protected abstract boolean getExpanded(Item item);
    /**
     * Returns a list of elements corresponding to expanded nodes in this
     * viewer's tree, including currently hidden ones that are marked as
     * expanded but are under a collapsed ancestor.
     * <p>
     * This method is typically used when preserving the interesting state of a
     * viewer; <code>setExpandedElements</code> is used during the restore.
     * </p>
     * 
     * @return the array of expanded elements
     * @see #setExpandedElements
     */
    public Object[] getExpandedElements() {
        ArrayList v = new ArrayList();
        internalCollectExpanded(v, getControl());
        return v.toArray();
    }
    /**
     * Returns whether the node corresponding to the given element is expanded
     * or collapsed.