Introduce Sky packaged apps.

sky/engine/core/script/dart_loader.cc

Index: sky/engine/core/script/dart_loader.cc
diff --git a/sky/engine/core/script/dart_loader.cc b/sky/engine/core/script/dart_loader.cc
index 9f6418167ec2aa7f2f7a705a8566f8302c9a1fb9..58fabf9eb4dc2c8d618e029399fe40b485dd410c 100644
--- a/sky/engine/core/script/dart_loader.cc
+++ b/sky/engine/core/script/dart_loader.cc
@@ -27,12 +27,24 @@ Dart_Handle CanonicalizeURL(DartState* state,
                             Dart_Handle library,
                             Dart_Handle url) {
   String string = StringFromDart(url);
+
   if (string.startsWith("dart:") || string.startsWith("mojo:"))
     return url;
   // TODO(dart): Figure out how 'package:' should work in sky.
   if (string.startsWith("package:")) {
-    string.replace("package:", "/packages/");
+    KURL baseUri = DOMDartState::Current()->document()->baseURI();
+    bool is_packaged_app = baseUri.string().startsWith("file://");

[eseidel, 2015/04/14 17:06:31]

Why aren't packaged apps just served over http locally?  That seems like it
would require the least amount of code modification?

+
+    if (is_packaged_app) {
+      // In packaged apps, |package:<foo>| is specified relative to the base URL
+      // of the application.
+      string.replace("package:", "");
+      string = KURL(baseUri, string).string();
+    } else {
+      string.replace("package:", "/packages/");
+    }
   }
+
   String library_url_string = StringFromDart(Dart_LibraryUrl(library));
   KURL library_url = KURL(ParsedURLString, library_url_string);
   KURL resolved_url = KURL(library_url, string);
@@ -60,7 +72,14 @@ class DartLoader::Job : public DartDependency,
  private:
   // MojoFetcher::Client
   void OnReceivedResponse(mojo::URLResponsePtr response) override {
-    if (response->status_code != 200) {
+    bool failed_load = response->status_code != 200;
+
+    // TODO(blundell): Why are successful loads of file:// URLs returning a 
+    // status code of 0?
+    if (response->status_code == 0) {

[eseidel, 2015/04/14 17:06:31]

Here again, instead of teaching Sky to understand a non-networked world, why not
just make packaged apps behave like a network?

+      failed_load = response->error != NULL;
+    }
+    if (failed_load) {
       loader_->DidFailJob(this);
       return;
     }