Dart: Runs dartanalyzer for the dart_pkg build rule.

mojo/dart/apptest/BUILD.gn

 # 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.
 
 import("//mojo/public/dart/rules.gni")
 
 dartzip_package("apptest") {
   uses_pub = true
   sources = [
     "lib/apptest.dart",
     "pubspec.yaml",
   ]
   deps = [
     "//mojo/public/dart",
   ]
 }
 
 dart_pkg("apptest_pkg") {
+  entrypoints = [ "lib/apptest.dart" ]
   sources = [
-    "lib/apptest.dart",
     "pubspec.yaml",
   ]
+  deps = [
+    "//mojo/public/dart:mojo",
+    "//third_party/dart-pkg",
+  ]
 }