Teach SkyView code path to print hello, world

sky/examples/raw/hello_world.dart

Index: sky/examples/raw/hello_world.dart
diff --git a/sky/engine/core/painting/Picture.idl b/sky/examples/raw/hello_world.dart
similarity index 78%
copy from sky/engine/core/painting/Picture.idl
copy to sky/examples/raw/hello_world.dart
index 0f618fdef72cafeff11960cb00f1fb24a959a6b0..cbf03f07841d22f07a6e6b99d25f11bd85e5de7c 100644
--- a/sky/engine/core/painting/Picture.idl
+++ b/sky/examples/raw/hello_world.dart
@@ -1,5 +1,7 @@
 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-interface Picture {
-};
+
+void main() {
+    print("Hello, world");
+}