Bug 167323 [Viewers]Open AbstractTreeViewer for external widget implementors
As reported by Ross Camara AbstractTreeViewer would work for nebula if we would open the API a bit. Boris and I decided that we will do this in 2 steps: 1. open the API 2. moving the Virtual-Support bits from TreeViewer to AbstractTreeViewer when the nebula grid provides virtual support.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
}
		IContentProvider cp = getContentProvider();
		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