Bug 174701 [Viewers] ViewerRow should be reused instead of connected to the Item
Currently we create a ViewerRow ver every Item we create this can degrade performance, we should cache the row and reuse it
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
if (cp instanceof ITreePathContentProvider) {
			ITreePathContentProvider tpcp = (ITreePathContentProvider) cp;
			if (path == null) {
				
				Widget w = findItem(element);
				if (w instanceof Item) {
					Item item = (Item) w;
					path = getTreePathFromItem(item);
				}
				if (path == null) {
					path = new TreePath(new Object[] { element });
				}
			}
			return tpcp.hasChildren(path);
		}
		if (cp instanceof ITreeContentProvider) {
			ITreeContentProvider tcp = (ITreeContentProvider) cp;
			return tcp.hasChildren(element);
		}
		return false;
	}
	/**
	 * Return whether the given element is expandable.
	 * 
	 * @param item
	 *            the tree item for the element
	 * @param parentPath
	 *            the parent path if it is knwon or <code>null</code> if it
	 *            needs to be determines
	 * @param element