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
&& !isExpandable((Item) widget, null, widget.getData())) {
				return;
			}
			createChildren(widget);
			if (widget instanceof Item) {
				setExpanded((Item) widget, true);
			}
			if (level == ALL_LEVELS || level > 1) {
				Item[] children = getChildren(widget);
				if (children != null) {
					int newLevel = (level == ALL_LEVELS ? ALL_LEVELS
							: level - 1);
					for (int i = 0; i < children.length; i++) {
						internalExpandToLevel(children[i], newLevel);
					}
				}
			}
		}
	}
	/**
	 * Non-recursively tries to find the given element as a child of the given
	 * parent (item or tree).
	 * 
	 * @param parent
	 *            the parent item
	 * @param element
	 *            the element
	 * @return Widget
	 */
	private Widget internalFindChild(Widget parent, Object element) {