code: function(callback, opt_this) {
        var curSlice = this;
  
        while (curSlice.parentSlice) {
          curSlice = curSlice.parentSlice;
          callback.call(opt_this, curSlice);
        }
      }
docs: Obtains the parents of a slice, from the most immediate to the root.
  
  For instance, E.iterateAllAncestors() in the following example:
  [     A          ]
  [ B][  D   ][ G  ]
  [C] [E][F]  [H]
  will pass D, then A to the provided callback, in the order from the
  leaves to the root.