Make it possible to run Sky apps offline

sky/services/viewport/viewport_observer.mojom

Index: sky/services/viewport/viewport_observer.mojom
diff --git a/sky/services/viewport/viewport_observer.mojom b/sky/services/viewport/viewport_observer.mojom
index 6271729b7110023b2fa0ad759dc1a89dbe33b6d2..ce86699be25aa654fb5565e345a4d1be18c782a5 100644
--- a/sky/services/viewport/viewport_observer.mojom
+++ b/sky/services/viewport/viewport_observer.mojom
@@ -10,5 +10,8 @@ import "sky/services/viewport/input_event.mojom";
 interface ViewportObserver {
   OnViewportMetricsChanged(int32 width, int32 height, float device_pixel_ratio);
   OnInputEvent(InputEvent event);
-  LoadURL(string url);
+
+  RunFromNetwork(string url);
+  RunFromFile(string main, string package_root);
+  RunFromSnapshot(handle<data_pipe_consumer> snapshot);
 };