Rename "inputPre" to "mainEditorPane".

dart/tests/try/paste_content_rewriting_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.
 
 // SharedOptions=--package-root=sdk/lib/_internal/
 
 library trydart.paste_test;
 
 import 'dart:html';
 import 'dart:async';
 
 import '../../site/try/src/interaction_manager.dart' show
     InteractionManager;
 
 import '../../site/try/src/ui.dart' show
-    inputPre,
+    mainEditorPane,
     observer;
 
 import '../../site/try/src/user_option.dart' show
     UserOption;
 
 import '../../pkg/expect/lib/expect.dart';
 import '../../pkg/async_helper/lib/async_helper.dart';
 
 main() {
   UserOption.storage = {};
 
   var interaction = new InteractionManager();
-  inputPre = new DivElement();
-  document.body.append(inputPre);
+  mainEditorPane = new DivElement();
+  document.body.append(mainEditorPane);
   observer = new MutationObserver(interaction.onMutation)
-      ..observe(inputPre, childList: true, characterData: true, subtree: true);
+      ..observe(mainEditorPane, childList: true, characterData: true, subtree: true);
 
-  inputPre.innerHtml = "<span><p>//...</p>}</span>";
+  mainEditorPane.innerHtml = "<span><p>//...</p>}</span>";
 
   asyncTest(() => new Future(() {
     print('Welcome to the future');
-    Expect.stringEquals('//...\n}\n', inputPre.text);
+    Expect.stringEquals('//...\n}\n', mainEditorPane.text);
   }).then((_) {
-    inputPre.innerHtml = 'someText';
+    mainEditorPane.innerHtml = 'someText';
     return new Future(() {
-      Expect.stringEquals('someText\n', inputPre.text);
+      Expect.stringEquals('someText\n', mainEditorPane.text);
 
       // Clear the DOM to work around a bug in test.dart.
       document.body.nodes.clear();
     });
   }));
 }