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
}
	/**
	 * Expands the root of the viewer's tree to the given level.
	 * 
	 * @param level
	 *            non-negative level, or <code>ALL_LEVELS</code> to expand all
	 *            levels of the tree
	 */
	public void expandToLevel(int level) {
		expandToLevel(getRoot(), level);
	}
	/**
	 * Expands all ancestors of the given element or tree path so that the given
	 * element becomes visible in this viewer's tree control, and then expands
	 * the subtree rooted at the given element to the given level.
	 * 
	 * @param elementOrTreePath
	 *            the element
	 * @param level
	 *            non-negative level, or <code>ALL_LEVELS</code> to expand all
	 *            levels of the tree
	 */
	public void expandToLevel(Object elementOrTreePath, int level) {
		Widget w = internalExpand(elementOrTreePath, true);
		if (w != null) {
			internalExpandToLevel(w, level);
		}
	}
	/**
	 * Fires a tree collapsed event. Only listeners registered at the time this