Serialize NativeBehavior for elements

tests/compiler/dart2js/serialization/helper.dart

Index: tests/compiler/dart2js/serialization/helper.dart
diff --git a/tests/compiler/dart2js/serialization/helper.dart b/tests/compiler/dart2js/serialization/helper.dart
index 3f2b42973917d8c67ce58b1a623808c7046befc8..e70b2ac106ef7ceafd85b25a5054577455b4e2d5 100644
--- a/tests/compiler/dart2js/serialization/helper.dart
+++ b/tests/compiler/dart2js/serialization/helper.dart
@@ -127,25 +127,39 @@ Future<SerializedData> serializeDartCore(
       print('Loading data from $file');
       serializedData = new SerializedData(uri, file.readAsStringSync());
     }
+  } else {
+    SerializationResult result = await serialize(Uris.dart_core, uri);
+    serializedData = result.serializedData;
   }
-  if (serializedData == null) {
-    Compiler compiler = compilerFor(
-        options: [Flags.analyzeAll]);
-    compiler.serialization.supportSerialization = true;
-    await compiler.run(Uris.dart_core);
-    BufferedEventSink sink = new BufferedEventSink();
-    compiler.serialization.serializeToSink(
-        sink, compiler.libraryLoader.libraries);
-    serializedData = new SerializedData(uri, sink.text);
-    if (arguments.saveSerializedData) {
-      File file = new File(arguments.serializedDataFileName);
-      print('Saving data to $file');
-      file.writeAsStringSync(serializedData.data);
-    }
+  if (arguments.saveSerializedData) {
+    File file = new File(arguments.serializedDataFileName);
+    print('Saving data to $file');
+    file.writeAsStringSync(serializedData.data);
   }
   return serializedData;
 }
 
+class SerializationResult {
+  final Compiler compiler;
+  final SerializedData serializedData;
+
+  SerializationResult(this.compiler, this.serializedData);
+}
+
+Future<SerializationResult> serialize(Uri entryPoint, [Uri dataUri]) async {
+  if (dataUri == null) {
+    dataUri = Uri.parse('memory:${DEFAULT_DATA_FILE_NAME}');
+  }
+  Compiler compiler = compilerFor(options: [Flags.analyzeAll]);
+  compiler.serialization.supportSerialization = true;
+  await compiler.run(entryPoint);
+  BufferedEventSink sink = new BufferedEventSink();
+  compiler.serialization.serializeToSink(
+      sink, compiler.libraryLoader.libraries);
+  SerializedData serializedData = new SerializedData(dataUri, sink.text);
+  return new SerializationResult(compiler, serializedData);
+}
+
 class SerializedData {
   final Uri uri;
   final String data;