Bug 65762 [Viewers] Need to back out of change to AbstractTreeViewer.isExpandable
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* Creates an abstract tree viewer. The viewer has no input, no content
	 * provider, a default label provider, no sorter, no filters, and has
	 * auto-expand turned off.
	 */
	protected AbstractTreeViewer() {
	    
	}
	/**
	 * Adds the given child elements to this viewer as children of the given
	 * parent element. If this viewer does not have a sorter, the elements are
	 * added at the end of the parent's list of children in the order given;
	 * otherwise, the elements are inserted at the appropriate positions.
	 * <p>
	 * This method should be called (by the content provider) when elements
	 * have been added to the model, in order to cause the viewer to accurately
	 * reflect the model. This method only affects the viewer, not the model.
	 * </p>
	 * 
	 * @param parentElement
	 *           the parent element
	 * @param childElements
	 *           the child elements to add
	 */
	public void add(Object parentElement, Object[] childElements) {
		Assert.isNotNull(parentElement);
		assertElementsNotNull(childElements);
		
		Widget widget = findItem(parentElement);
		
		if (widget == null)