Bug 211991 Page header items when in a grid within a grid disappear on runtime render
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/layout/html/HTMLPageLM.java
public void startContent( IContent content )
		{
			if ( current != null )
			{
				if(content!=null)
				{
					current.children.add( content );
					current = new BufferNode(content, current);
					nodes.add( current );
				}
				else
				{
					current = null;
				}
			}
				
		}
		public void endContent( IContent content )
		{
			if(current!=null)
			{
				if(content!=null)
				{
					current = current.parent;
				}
			}
		}
	}
	
	class BufferNode