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
CustomHashtable expandedTreePaths, Widget widget,
			TreePath currentPath) {
		Item[] items = getChildren(widget);
		for (int i = 0; i < items.length; i++) {
			Item item = items[i];
			Object data = item.getData();
			TreePath childPath = data == null ? null : currentPath
					.createChildPath(data);
			if (data != null && childPath != null) {
				
				
				boolean expanded = expandedTreePaths.remove(childPath) != null;
				if (expanded != getExpanded(item)) {
					if (expanded) {
						createChildren(item);
					}
					setExpanded(item, expanded);
				}
			}
			internalSetExpandedTreePaths(expandedTreePaths, item, childPath);
		}
	}
	/**
	 * Return whether the tree node representing the given element or path can
	 * be expanded. Clients should query expandablity by path if the viewer's
	 * content provider is an {@link ITreePathContentProvider}.
	 * <p>
	 * The default implementation of this framework method calls
	 * <code>hasChildren</code> on this viewer's content provider. It may be
	 * overridden if necessary.