code: function mxTooltipHandler(graph, delay)
  {
  	if (graph != null)
  	{
  		this.graph = graph;
  		this.delay = delay || 500;
  		this.graph.addMouseListener(this);
  	}
  }
docs: Copyright (c) 2006-2015, JGraph Ltd
  Copyright (c) 2006-2015, Gaudenz Alder
   
  Class: mxTooltipHandler
  
  Graph event handler that displays tooltips. <mxGraph.getTooltip> is used to
  get the tooltip for a cell or handle. This handler is built-into
  <mxGraph.tooltipHandler> and enabled using <mxGraph.setTooltips>.
  
  Example:
  
  (code>
  new mxTooltipHandler(graph);
  (end)
  
  Constructor: mxTooltipHandler
  
  Constructs an event handler that displays tooltips with the specified
  delay (in milliseconds). If no delay is specified then a default delay
  of 500 ms (0.5 sec) is used.
  
  Parameters:
  
  graph - Reference to the enclosing <mxGraph>.
  delay - Optional delay in milliseconds.