Fix Try Dart newline handling on IE11.

tests/try/web/cursor_position_test.dart

Index: tests/try/web/cursor_position_test.dart
===================================================================
--- tests/try/web/cursor_position_test.dart	(revision 39473)
+++ tests/try/web/cursor_position_test.dart	(working copy)
@@ -13,9 +13,18 @@
       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>[