Fix issues that broke editing on browsers without Shadow DOM support.

dart/tests/try/paste_content_rewriting_test.dart

Index: dart/tests/try/paste_content_rewriting_test.dart
diff --git a/dart/tests/try/paste_content_rewriting_test.dart b/dart/tests/try/paste_content_rewriting_test.dart
index d04e7acbc03078a0eed7a29a13f8184e1a4bb995..6583c75f06720c4db5aebce3553b7eec63dab6a8 100644
--- a/dart/tests/try/paste_content_rewriting_test.dart
+++ b/dart/tests/try/paste_content_rewriting_test.dart
@@ -46,9 +46,8 @@ Future runTests() {
     String key = keys.current;
     print('Checking $key');
     queryDiagnosticNodes().forEach((Node node) {
-      node.parent.insertBefore(
-          new Text('<DIAGNOSTIC>'), node.parent.firstChild);
-      node.replaceWith(new Text('</DIAGNOSTIC>'));
+      node.parent.append(new Text('</DIAGNOSTIC>'));
+      node.replaceWith(new Text('<DIAGNOSTIC>'));

[ahe, 2014/07/04 13:52:00]

This code replaces diagnostics with <DIAGNOSTIC>...</DIAGNOSTIC>.

Before it was operating on:

<a>...<span>tip</span></a>

Now it looks like:

<a><span>tip</span>...</a>

       observer.takeRecords(); // Discard mutations.
     });
     Expect.stringEquals(tests[key], mainEditorPane.text);