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
private Object element;
		private Item item;
		UpdateItemSafeRunnable(Item item, Object element) {
			this.item = item;
			this.element = element;
		}
		public void run() {
			doUpdateItem(item, element);
		}
	}
	/**
	 * 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>