Bug 172019 [Viewers] Plus sign doesn't disappear when using deferred content providers
3.3 M4 Use a tree viewer with a content provider using IDeferredWorkbenchAdapter and DeferredTreeContentManager. When fetchDeferredChildren is call and no elements are reported to the element collector the plus sign of the node doesn't disappear. This work without problems under Windows and Mac/OS (e.g. the plus sign disappears).
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
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);
		}
	}
	/**
	 * Creates all children for the given widget.
	 * <p>
	 * The default implementation of this framework method assumes that
	 * <code>widget.getData()</code> returns the element corresponding to the
	 * node. Note: the node is not visually expanded! You may have to call
	 * <code>parent.setExpanded(true)</code>.
	 * </p>
	 * 
	 * @param widget