Tokenize one line at a time.

dart/site/try/src/ui.dart

 // Copyright (c) 2013, 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.
 
 library trydart.ui;
 
 import 'dart:html';
 
 import 'dart:async' show
     Future,
@@ skipping 86 matching lines @@
 buildUI() {
   interaction = new InteractionManager();
 
   CompilationUnit.onChanged.listen(interaction.onCompilationUnitChanged);
 
   window.localStorage['currentSample'] = '$currentSample';
 
   buildCode(interaction);
 
   (mainEditorPane = new DivElement())
-      ..classes.add('well')
+      ..classes.addAll(['well', 'mainEditorPane'])
       ..style.backgroundColor = currentTheme.background.color
       ..style.color = currentTheme.foreground.color
-      ..style.overflow = 'visible'
-      ..style.whiteSpace = 'pre'
       ..style.font = codeFont
       ..spellcheck = false;
 
   mainEditorPane
       ..contentEditable = 'true'
       ..onKeyDown.listen(interaction.onKeyUp)
       ..onInput.listen(interaction.onInput);
 
   document.onSelectionChange.listen(interaction.onSelectionChange);
 
@@ skipping 362 matching lines @@
     window.localStorage['compilationPaused'] = '$compilationPaused';
     window.localStorage['codeFont'] = '$codeFont';
 
     dialog.style.height = '0px';
   }
   form.onSubmit.listen(onSubmit);
 
   var doneButton = document.getElementById('settings-done');
   doneButton.onClick.listen(onSubmit);
 }