Revert pub to script snapshots in the GN build. Fixes #28346.

utils/application_snapshot.gni

Index: utils/application_snapshot.gni
diff --git a/utils/application_snapshot.gni b/utils/application_snapshot.gni
index 8899703e912870b3f2e223d0accaa29f2ce1b379..ffc0653321bb1c0b5eae4f761f4025b96f827ffe 100644
--- a/utils/application_snapshot.gni
+++ b/utils/application_snapshot.gni
@@ -49,3 +49,48 @@ template("application_snapshot") {
            ] + training_args
   }
 }
+
+# TODO(28368): Revert to application snapshot after spawnUri issue is fixed. 
+template("script_snapshot") {
+  assert(defined(invoker.main_dart), "Must specify 'main_dart'")
+  assert(defined(invoker.training_args), "Must specify 'training_args'")

[zra, 2017/01/12 21:12:41]

Why does a script snapshot need training args?

[rmacnak, 2017/01/13 18:47:41]

It doesn't. This was a quick fix and removed in
https://codereview.chromium.org/2628283002.

+  main_dart = invoker.main_dart
+  training_args = invoker.training_args
+  name = target_name
+  if (defined(invoker.name)) {
+    name = invoker.name
+  }
+  extra_deps = []
+  if (defined(invoker.deps)) {
+    extra_deps += invoker.deps
+  }
+  extra_inputs = []
+  if (defined(invoker.inputs)) {
+    extra_inputs += invoker.inputs
+  }
+  compiled_action(target_name) {
+    tool = get_path_info("$_dart_root/runtime/bin:dart", "abspath")
+    deps = extra_deps + [ "$_dart_root/pkg:pkg_files_stamp" ]
+
+    inputs = extra_inputs + [
+               "$_dart_root/sdk/lib/_internal/sdk_library_metadata/lib/libraries.dart",
+               "$root_gen_dir/pkg_files.stamp",
+             ]
+
+    output = "$root_gen_dir/$name.dart.snapshot"
+    outputs = [
+      output,
+    ]
+
+    dot_packages = rebase_path("$_dart_root/.packages")
+    abs_output = rebase_path(output)
+    main_file = rebase_path(main_dart)
+
+    args = [
+             "--packages=$dot_packages",
+             "--snapshot=$abs_output",
+             "--snapshot-kind=script",
+             main_file,
+           ] + training_args
+  }
+}