Fix vm tests: introduce a hybrid file system so that the vm tests can find the

utils/application_snapshot.gni

 # Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 import("../build/compiled_action.gni")
 
 _dart_root = get_path_info("..", "abspath")
 
 declare_args() {
   # Default to building app-jit snapshots. The simulator and cross builds
   # override this to script snapshots to cut down on build time.
   dart_snapshot_kind = "app-jit"
 }
 
 template("application_snapshot") {
   assert(defined(invoker.main_dart), "Must specify 'main_dart'")
   assert(defined(invoker.training_args), "Must specify 'training_args'")
   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 = []
+  extra_inputs = [main_dart]

[Siggi Cherem (dart-lang), 2017/05/25 18:47:55]

Not sure if this is the proper way to fix it, but I noticed that changing
kernel-service.dart was not enough to trigger a rebuild of the snapshot, this
fixes that.

   if (defined(invoker.inputs)) {
     extra_inputs += invoker.inputs
   }
   compiled_action(target_name) {
     tool = "$_dart_root/runtime/bin:dart"
     deps = extra_deps + [ "$_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",
@@ skipping 16 matching lines @@
                main_file ]
       assert(training_args != "", "Ignoring unused argument")
     } else if (dart_snapshot_kind == "app-jit") {
       args += ["--snapshot-kind=app-jit",
                main_file ] + training_args
     } else {
       assert(false, "Bad dart_snapshot_kind: $dart_snapshot_kind")
     }
   }
 }