Add a line number filter for layout tests. Suppress/fix Dartium layout tests.

LayoutTests/dart/dom/DOMMap.dart

 import 'package:expect/expect.dart';
 import 'package:unittest/html_config.dart';
 import 'package:unittest/unittest.dart';
 import 'dart:html';
 import 'dart:isolate';
 
 main() {
   useHtmlConfiguration(true);
   test('ElementsIdentity', () {
+    // Except with Dartium/JS-interop we don't get identity, we'll have
+    // to settle for equality.
     DivElement div = new Element.tag('div');
     div.id = 'test';
     document.body.nodes.add(div);
 
     Element element = document.query('#test');
-    Expect.identical(div, element);
+    Expect.equals(div, element);
   });
   test('TwoIsolates', () {
     // Test that we can access the same DOM nodes from different isolates.
     // FIXME: uncomment when we have DOM isolates.
     /*
     SendPort port = spawnFunction(isolateEntry);
     Element testDiv = document.query('#test_div');
     Expect.equals('Hello from Dart Frame', testDiv.innerHtml);
     document.body.removeChild(testDiv);
     */
   });
 }
 
 void isolateEntry() {
   Element element = new Element.tag('div');
   element.id = 'test_div';
   element.innerHtml = 'Hello from Dart isolate';
   document.body.nodes.add(element);
 }