Program: 81812
Project: 81812
Buggy source:
public void render(SafeHtmlBuilder sb,List<C> values,int start,SelectionModel<? super C> selectionModel){
  CellTree.Style style=nodeView.tree.getStyle();
  String itemValueStyle=style.cellTreeItemValue();
  String selectedStyle="String_Node_Str" + style.cellTreeSelectedItem();
  String itemStyle=style.cellTreeItem();
  String itemImageValueStyle="String_Node_Str" + style.cellTreeItemImageValue();
  String openStyle="String_Node_Str" + style.cellTreeOpenItem();
  String topStyle="String_Node_Str" + style.cellTreeTopItem();
  String topImageValueStyle="String_Node_Str" + style.cellTreeTopItemImageValue();
  boolean isRootNode=nodeView.isRootNode();
  SafeHtml openImage=nodeView.tree.getOpenImageHtml(isRootNode);
  SafeHtml closedImage=nodeView.tree.getClosedImageHtml(isRootNode);
  int imageWidth=nodeView.tree.getImageWidth();
  String paddingDirection=LocaleInfo.getCurrentLocale().isRTL() ? "String_Node_Str" : "String_Node_Str";
  int paddingAmount=imageWidth * nodeView.depth;
  Set<Object> openNodes=new HashSet<Object>();
  int childCount=nodeView.getChildCount();
  int end=start + values.size();
  for (int i=start; i < end && i < childCount; i++) {
    CellTreeNodeView<?> child=nodeView.getChildNode(i);
    if (child.isOpen()) {
      openNodes.add(child.getValueKey());
    }
  }
  ProvidesKey<C> keyProvider=nodeInfo.getProvidesKey();
  TreeViewModel model=nodeView.tree.getTreeViewModel();
  for (int i=start; i < end; i++) {
    C value=values.get(i - start);
    Object key=keyProvider.getKey(value);
    boolean isOpen=openNodes.contains(key);
    StringBuilder outerClasses=new StringBuilder(itemStyle);
    if (isOpen) {
      outerClasses.append(openStyle);
    }
    if (isRootNode) {
      outerClasses.append(topStyle);
    }
    if (selectionModel != null && selectionModel.isSelected(value)) {
      outerClasses.append(selectedStyle);
    }
    StringBuilder innerClasses=new StringBuilder(itemStyle);
    innerClasses.append(itemImageValueStyle);
    if (isRootNode) {
      innerClasses.append(topImageValueStyle);
    }
    SafeHtml image;
    if (isOpen) {
      image=openImage;
    }
 else     if (model.isLeaf(value)) {
      image=LEAF_IMAGE;
    }
 else {
      image=closedImage;
    }
    SafeHtmlBuilder cellBuilder=new SafeHtmlBuilder();
    Context context=new Context(i,0,key);
    cell.render(context,value,cellBuilder);
    SafeStyles innerPadding=SafeStylesUtils.fromTrustedString("String_Node_Str" + paddingDirection + "String_Node_Str"+ imageWidth+ "String_Node_Str");
    SafeHtml innerDiv=template.innerDiv(innerPadding,innerClasses.toString(),image,itemValueStyle,cellBuilder.toSafeHtml());
    SafeStyles outerPadding=SafeStylesUtils.fromTrustedString("String_Node_Str" + paddingDirection + "String_Node_Str"+ paddingAmount+ "String_Node_Str");
    sb.append(template.outerDiv(outerPadding,outerClasses.toString(),innerDiv));
  }
}

Fixed version (ground truth):
@Override public void render(SafeHtmlBuilder sb,List<C> values,int start,SelectionModel<? super C> selectionModel){
  CellTree.Style style=nodeView.tree.getStyle();
  String itemValueStyle=style.cellTreeItemValue();
  String selectedStyle="String_Node_Str" + style.cellTreeSelectedItem();
  String itemStyle=style.cellTreeItem();
  String itemImageValueStyle="String_Node_Str" + style.cellTreeItemImageValue();
  String openStyle="String_Node_Str" + style.cellTreeOpenItem();
  String topStyle="String_Node_Str" + style.cellTreeTopItem();
  String topImageValueStyle="String_Node_Str" + style.cellTreeTopItemImageValue();
  boolean isRootNode=nodeView.isRootNode();
  SafeHtml openImage=nodeView.tree.getOpenImageHtml(isRootNode);
  SafeHtml closedImage=nodeView.tree.getClosedImageHtml(isRootNode);
  int imageWidth=nodeView.tree.getImageWidth();
  String paddingDirection=LocaleInfo.getCurrentLocale().isRTL() ? "String_Node_Str" : "String_Node_Str";
  int paddingAmount=imageWidth * nodeView.depth;
  Set<Object> openNodes=new HashSet<Object>();
  int childCount=nodeView.getChildCount();
  int end=start + values.size();
  for (int i=start; i < end && i < childCount; i++) {
    CellTreeNodeView<?> child=nodeView.getChildNode(i);
    if (child.isOpen()) {
      openNodes.add(child.getValueKey());
    }
  }
  ProvidesKey<C> keyProvider=nodeInfo.getProvidesKey();
  TreeViewModel model=nodeView.tree.getTreeViewModel();
  for (int i=start; i < end; i++) {
    C value=values.get(i - start);
    Object key=keyProvider.getKey(value);
    boolean isOpen=openNodes.contains(key);
    StringBuilder outerClasses=new StringBuilder(itemStyle);
    if (isOpen) {
      outerClasses.append(openStyle);
    }
    if (isRootNode) {
      outerClasses.append(topStyle);
    }
    if (selectionModel != null && selectionModel.isSelected(value)) {
      outerClasses.append(selectedStyle);
    }
    StringBuilder innerClasses=new StringBuilder(itemStyle);
    innerClasses.append(itemImageValueStyle);
    if (isRootNode) {
      innerClasses.append(topImageValueStyle);
    }
    SafeHtml image;
    if (isOpen) {
      image=openImage;
    }
 else     if (model.isLeaf(value)) {
      image=LEAF_IMAGE;
    }
 else {
      image=closedImage;
    }
    SafeHtmlBuilder cellBuilder=new SafeHtmlBuilder();
    Context context=new Context(i,0,key);
    cell.render(context,value,cellBuilder);
    SafeStyles innerPadding=SafeStylesUtils.fromTrustedString("String_Node_Str" + paddingDirection + "String_Node_Str"+ imageWidth+ "String_Node_Str");
    SafeHtml innerDiv=template.innerDiv(innerPadding,innerClasses.toString(),image,itemValueStyle,cellBuilder.toSafeHtml());
    SafeStyles outerPadding=SafeStylesUtils.fromTrustedString("String_Node_Str" + paddingDirection + "String_Node_Str"+ paddingAmount+ "String_Node_Str");
    sb.append(template.outerDiv(outerPadding,outerClasses.toString(),innerDiv));
  }
}