This test has the following code:

  var layerTree = internals.layerTreeAsText(document, internals.LAYER_TREE_INCLUDES_ROOT_LAYER);
  if (layerTree.indexOf('\n    {\n\n    }\n') != -1)
      layerTree = internals.layerTreeAsText(document, 1 | internals.LAYER_TREE_INCLUDES_ROOT_LAYER);

It doesn't make sense to call layerTreeAsText twice, and there are no comments to indicate the significance of the string '\n    {\n\n    }\n'.  We should decide what flags are appropriate, and pass them the first time.

(Further note: http://crrev.com/1151153003 seems to have been landed TBR without code review.  I think this is not an appropriate use of TBR per https://chromium.googlesource.com/chromium/src/+/master/docs/code_reviews.md#TBR-To-Be-Reviewed.  Changes to layout tests should go through the same review process as normal code.)