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
} else {
			
			super.associate(element, item);
		}
	}
	/**
	 * Collapses all nodes of the viewer's tree, starting with the root. This
	 * method is equivalent to <code>collapseToLevel(ALL_LEVELS)</code>.
	 */
	public void collapseAll() {
		Object root = getRoot();
		if (root != null) {
			collapseToLevel(root, ALL_LEVELS);
		}
	}
	/**
	 * Collapses the subtree rooted at the given element or tree path to the
	 * given level.
	 * 
	 * @param elementOrTreePath
	 *            the element or tree path
	 * @param level
	 *            non-negative level, or <code>ALL_LEVELS</code> to collapse
	 *            all levels of the tree
	 */
	public void collapseToLevel(Object elementOrTreePath, int level) {
		Assert.isNotNull(elementOrTreePath);
		Widget w = internalGetWidgetToSelect(elementOrTreePath);
		if (w != null) {
			internalCollapseToLevel(w, level);