code: function(topIndex, callback) {
  			if (!this._clientDiv) { return; }
  			this._scrollViewAnimated(0, this._getLinePixel(Math.max(0, topIndex)) - this._getScroll().y, callback);
  		}
docs: Sets the top index.
  <p>
  The top index is the line that is currently at the top of the text view.  This
  line may be partially visible depending on the vertical scroll of the view.
  </p>
  
  @param {Number} topIndex the index of the top line.
  @param {Function} [callback] if callback is specified and <code>scrollAnimation</code> is not zero, view scrolling is animated and
  the callback is called when the animation is done. Otherwise, callback is callback right away.
  
  @see orion.editor.TextView#getBottomIndex
  @see orion.editor.TextView#getTopIndex