New Twiddle

controllers.application.js

import Ember from 'ember';
import FactoryGuy, {manualSetup} from 'ember-data-factory-guy';

export default Ember.Controller.extend({
    
    data: { fg: FactoryGuy,
            text: 'Single child node (has tooltip)',
            type: 'single-child',
          }
});

helpers.fixed-grid-layout.js

import Ember from 'ember';
import FactoryGuy from 'ember-data-factory-guy';
import Grid from 'ember-collection/layouts/grid';

export default Ember.Helper.helper(function (params, hash) {
  //return new Grid(params[0], params[1]);
});

templates.application.hbs

<div class="sample-tree">
<tr>
  <td>
    {{#ember-collection class="collection base-entry-list" items=rows cell-layout=(fixed-grid-layout 335 37) as |row index|}}
     <div class="left-row">{{row}}</div>
    {{/ember-collection}}
  </td>         
  <td>
    {{#ember-collection class="collection version-entry-list" items=rows cell-layout=(fixed-grid-layout null 37) as |row index|}}
     <div class="right-row">{{row}}</div>
    {{/ember-collection}}
  </td>
</tr>        
</div>

twiddle.json

{
  "version": "0.10.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.9.0",
    "ember-data": "2.9.0"    
  },
  "addons": {
    "ember-collection": "1.0.0-alpha.7",
    "ember-data-factory-guy": "2.9.3"
  }
}