code: function _waitForBody(options) {
              options = options || {};
              var onready = options.onready;
              var doc = options.doc || root.document;
              var delay = options.delay;
  
              function _ready() {
                  if (doc.body) {
                      onready();
                  }
                  else {
                      PostMessageUtilities.delay(_ready, delay || DEFAULT_BODY_LOAD_DELAY);
                  }
              }
  
              PostMessageUtilities.delay(_ready, delay || false);
          }
docs: Method to enable running a callback once the document body is ready
  @param {Object} [options] Configuration options
  @param {Function} options.onready - the callback to run when ready
  @param {Object} [options.doc = root.document] - document to refer to
  @param {Number} [options.delay = 0] - milliseconds to delay the execution
  @private