Bug 158778 [Viewers] request for remove(parent, index) API on tree viewer
3.3 It would be helpful to have a 'remove(Object parent, int index)' method on the tree viewer to complement that 'replace(...)' and 'setChildCount(...)' APIs. The debug platform requires such a method to implement filtering in virtual tree views. Rather than performing a 'replace/remove' based on elements, the content provider can make one atomic call to remove an element at a specific index.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
if (paths.length > 0) {
				if (paths[0].getSegmentCount() == 0) {
					return getInput();
				}
				return paths[0].getLastSegment();
			}
		}
		if (cp instanceof ITreeContentProvider) {
			ITreeContentProvider tcp = (ITreeContentProvider) cp;
			return tcp.getParent(elementOrTreePath);
		}
		return null;
	}
	/**
	 * 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;
			if (treePath.getSegmentCount() == 0) {
				return null;
			}
			Widget[] candidates = findItems(treePath.getLastSegment());
			for (int i = 0; i < candidates.length; i++) {