Bug 125272 [Viewers] AbstractTreeViewer needs remove(Object parentElement, Object[] childElements)
There is an add(Object parentElement, Object[] childElements) but no corresponding remove(). Without this method, if you have an element that appears under multiple parents, the only way to get model and viewer in sync after removing the element from just one of its parents is calling refresh().
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* <code>null</code>.
	 * 
	 * @param elementOrTreePath
	 * @return the parent element, or parent path, or <code>null</code>
	 */ 
    protected Object getParentElement(Object elementOrTreePath) {
    	if(elementOrTreePath instanceof TreePath) {
    		TreePath treePath = (TreePath)elementOrTreePath;
    		if(treePath.getSegmentCount() <= 1) {
    			return null;
    		}
			return (treePath).getParentPath();
    	}
        ITreeContentProvider cp = (ITreeContentProvider) getContentProvider();
        if (cp == null) {
            return null;
        }
        return cp.getParent(elementOrTreePath);
	}
	/**
     * Returns the widget to be selected for the given element or tree path.
     * 
     * @param elementOrTreePath the element or tree path to select
     * @return the widget to be selected, or <code>null</code> if not found
     * 
     * @since 3.1
     */
	protected Widget internalGetWidgetToSelect(Object elementOrTreePath) {
		if(elementOrTreePath instanceof TreePath) {
			TreePath treePath = (TreePath) elementOrTreePath;