Bug 305739 [viewers] #expandToLevel(Object, level) retrieves all children when virtual
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TreeViewer.java
fireTreeExpanded(new TreeExpansionEvent(this, event.item
						.getData()));
			}
			return;
		}
		super.handleTreeExpand(event);
	}
	
	protected void handleTreeCollapse(TreeEvent event) {
		
		
		if( isCellEditorActive() ) {
			applyEditorValue();
		}
		
		super.handleTreeCollapse(event);
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jface.viewers.AbstractTreeViewer#setContentProvider(org.eclipse.jface.viewers.IContentProvider)
	 */
	public void setContentProvider(IContentProvider provider) {
		contentProviderIsLazy = (provider instanceof ILazyTreeContentProvider)
				|| (provider instanceof ILazyTreePathContentProvider);
		contentProviderIsTreeBased = provider instanceof ILazyTreePathContentProvider;
		super.setContentProvider(provider);
	}
	/**
	 * For a TreeViewer with a tree with the VIRTUAL style bit set, inform the
	 * viewer about whether the given element or tree path has children. Avoid
	 * calling this method if the number of children has already been set.