anchor.diff:      // The padding applies to the toolbar and tabbar, not the flexible space.
       // The incoming padding parameter's top value typically equals the height
       // of the status bar - so that the toolbar appears below the status bar.
  -    EdgeInsets combinedPadding = new EdgeInsets.symmetric(horizontal: 8.0);
  -    if (padding != null)
  -      combinedPadding += padding;
       appBar = new Padding(
  -      padding: combinedPadding,
  +      padding: padding,
         child: appBar
       );
   
       // If the appBar's height shrinks below collapsedHeight, it will be clipped and bottom
       // justified. This is so that the toolbar and the tabbar appear to move upwards as
       // the appBar's height is reduced below collapsedHeight.
  -    final double paddedCollapsedHeight = collapsedHeight + combinedPadding.top + combinedPadding.bottom;
  +    final double paddedCollapsedHeight = collapsedHeight + padding.top + padding.bottom;
       if (size.height < paddedCollapsedHeight) {
         appBar = new ClipRect(
           child: new OverflowBox(
  
positive.code:     if (actions != null)
        toolBarRow.addAll(actions);
  
      Widget toolBar = new Row(children: toolBarRow);
  
      if (effectiveCenterTitle && centerWidget != null) {
        toolBar = new Stack(
  
negative.code: /// The AppBar displays the toolbar widgets, [leading], [title], and
  /// [actions], above the [bottom] (if any). If a [flexibleSpace] widget is
  /// specified then it is stacked behind the toolbar and the bottom widget.
  ///
  /// The [Scaffold] typically creates the app bar with an initial height equal to
  /// [expandedHeight]. If the [Scaffold.appBarBehavior] is set then the
  /// AppBar's [collapsedHeight] and [bottomHeight] define how small the app bar
  /// will become when the application is scrolled.
  