Load time improvements (fixes #140)

lib/runtime/messages_widget.dart

Index: lib/runtime/messages_widget.dart
diff --git a/lib/runtime/messages_widget.dart b/lib/runtime/messages_widget.dart
index 469eddab21978e09e1fcd590af23774ba915b426..e2930c9e96721969bb9e959d2b894fb2a00593a9 100644
--- a/lib/runtime/messages_widget.dart
+++ b/lib/runtime/messages_widget.dart
@@ -15,7 +15,10 @@ import 'package:path/path.dart' as path;
 import 'package:source_span/source_span.dart';
 import 'package:dev_compiler/src/summary.dart';
 
-main() async => displayMessages(await HttpRequest.getString('messages.json'));
+main() async {
+  await window.animationFrame;
+  displayMessages(await HttpRequest.getString('messages.json'));
+}
 
 void displayMessages(String data) {
   var summary = GlobalSummary.parse(JSON.decode(data));