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/TreeViewer.java
/**
	 * Returns whether there is an active cell editor.
	 * 
	 * @return <code>true</code> if there is an active cell editor, and
	 *         <code>false</code> otherwise
	 * @since 3.1
	 */
	public boolean isCellEditorActive() {
		return treeViewerImpl.isCellEditorActive();
	}
	/*
	 * (non-Javadoc) Method declared in AbstractTreeViewer.
	 */
	protected Item newItem(Widget parent, int flags, int ix) {
		TreeItem item;
		if (parent instanceof TreeItem) {
			item = (TreeItem) createNewRowPart(getRowPartFromItem(parent),
					flags, ix).getItem();
		} else {
			item = (TreeItem) createNewRowPart(null, flags, ix).getItem();
		}
		return item;
	}
	/*
	 * (non-Javadoc) Method declared in AbstractTreeViewer.
	 */
	protected void removeAll(Control widget) {
		((Tree) widget).removeAll();
	}
	/**