Synchronize GN build configuration with Chrome

mojo/public/dart/rules.gni

 # 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.
 
 # This file has rules for making Dart packages and Dart-based Mojo applications.
 # The entrypoint is the dart_pkg rule.
 
 import("../mojo.gni")
 import("//build/module_args/mojo.gni")
 import("//build/module_args/dart.gni")
@@ skipping 65 matching lines @@
       "--output",
       rebase_path(bundle),
     ]
 
     deps = [
       ":gen_${bundle_prefix}_snapshot",
     ]
   }
 
   group(target_name) {
-    deps = [
+    public_deps = [
       ":gen_${bundle_prefix}_bundle",
     ]
   }
 }
 
 template("dartx_application") {
   dartx_name = "${target_name}_dartx"
 
   dartx(dartx_name) {
     main_dart = invoker.main_dart
@@ skipping 347 matching lines @@
   group(target_name) {
     deps = []
     foreach(package_dir, packages) {
       deps += [ ":$package_dir" ]
     }
     if (defined(invoker.deps)) {
       deps += invoker.deps
     }
   }
 }