Fix Try Dart newline handling on IE11.

tests/try/web/cursor_position_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Test that cursor positions are correctly updated after adding new content.
 
 import 'test_try.dart';
 
 void main() {
   InteractionManager interaction = mockTryDartInteraction();
 
   TestCase twoLines =
       new TestCase('Test adding two lines programmatically.', () {
         clearEditorPaneWithoutNotifications();
         mainEditorPane.appendText('\n\n');
-        Text text = mainEditorPane.firstChild;
-        window.getSelection().collapse(text, 1);
-        checkSelectionIsCollapsed(text, 1);
+        var textOrBr = mainEditorPane.firstChild;
+        if (textOrBr is Text) {
+          window.getSelection().collapse(textOrBr, 1);
+          checkSelectionIsCollapsed(textOrBr, 1);
+        } else {
+          // This else-branch accomodates IE11, which
+          // puts <BR> instead of '\n' in content-editable Divs.
+          var range = document.createRange()..selectNode(textOrBr);
+          (window.getSelection())..addRange(range)
+                                 ..collapseToEnd();
+          checkSelectionIsCollapsed(mainEditorPane, 1);
+        }
       }, checkAtBeginningOfSecondLine);
 
   runTests(<TestCase>[
     twoLines,
 
     new TestCase('Test adding a new text node.', () {
       // This test relies on the previous test leaving two lines.
       Text text = new Text('fisk');
       window.getSelection().getRangeAt(0).insertNode(text);
       window.getSelection().collapse(text, text.length);
@@ skipping 76 matching lines @@
 
 class MockKeyboardEvent extends KeyEvent {
   final int keyCode;
 
   MockKeyboardEvent(String type, {int keyCode})
       : this.keyCode = keyCode,
         super.wrap(new KeyEvent(type, keyCode: keyCode));
 
   bool getModifierState(String keyArgument) => false;
 }