Use serialized scope info to test incremental compiler.

dart/pkg/dart2js_incremental/lib/dart2js_incremental.dart

Index: dart/pkg/dart2js_incremental/lib/dart2js_incremental.dart
diff --git a/dart/pkg/dart2js_incremental/lib/dart2js_incremental.dart b/dart/pkg/dart2js_incremental/lib/dart2js_incremental.dart
index d1a3cb675226d71f6746257cb91d7007f40c2801..d5074f8bbddefd86c50f3535e5cd0c7d5b68cf34 100644
--- a/dart/pkg/dart2js_incremental/lib/dart2js_incremental.dart
+++ b/dart/pkg/dart2js_incremental/lib/dart2js_incremental.dart
@@ -75,6 +75,10 @@ class IncrementalCompiler {
     }
   }
 
+  LibraryElement get mainApp => _compiler.mainApp;
+
+  Compiler get compiler => _compiler;
+
   Future<bool> compile(Uri script) {
     return _reuseCompiler(null).then((Compiler compiler) {
       _compiler = compiler;