Devtools: DataGrid: do not render hidden columns.

LayoutTests/inspector/profiler/heap-snapshot-test.js

 var initialize_HeapSnapshotTest = function() {
 
 InspectorTest.createHeapSnapshotMockFactories = function() {
 
 InspectorTest.createJSHeapSnapshotMockObject = function()
 {
     return {
         _rootNodeIndex: 0,
         _nodeTypeOffset: 0,
         _nodeNameOffset: 1,
@@ skipping 559 matching lines @@
         setTimeout(callCallback, 0);
     }
     parent.addEventListener(WebInspector.HeapSnapshotGridNode.Events.PopulateComplete, populateComplete, this);
     row[buttonName].click();
 };
 
 InspectorTest.columnContents = function(column, row)
 {
     // Make sure invisible nodes are removed from the view port.
     this._currentGrid().updateVisibleNodes();
+    var columnOrdinal = InspectorTest.viewColumns().indexOf(column);
     var result = [];
     var parent = row || this._currentGrid().rootNode();
     for (var node = parent.children[0]; node; node = node.traverseNextNode(true, parent, true)) {
         if (!node.selectable)
             continue;
-        var content = node.element.children[column.ordinal];
+        var content = node.element.children[columnOrdinal];
         // Do not inlcude percents
         if (content.firstElementChild)
             content = content.firstElementChild;
         result.push(content.textContent);
     }
     return result;
 };
 
 InspectorTest.countDataRows = function(row, filter)
 {
@@ skipping 129 matching lines @@
         function sortingComplete()
         {
             dataGrid.removeEventListener(WebInspector.HeapSnapshotSortableDataGrid.Events.SortingComplete, sortingComplete, null);
             callback();
         }
         dataGrid.addEventListener(WebInspector.HeapSnapshotSortableDataGrid.Events.SortingComplete, sortingComplete, null);
     }
 };
 
 };