Add package_config to DEPS.

DEPS

 # Copyright (c) 2012, 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.
 
 vars = {
   # The dart_root is the root of our sdk checkout. This is normally
   # simply sdk, but if using special gclient specs it can be different.
   "dart_root": "sdk",
 
   # The svn location to pull out dependencies from
@@ skipping 42 matching lines @@
   "logging_rev": "@85d83e002670545e9039ad3985f0018ab640e597",
   "markdown_rev": "@56b0fd6c018d6103862d07e8e27407b9ea3b963d",
   "matcher_tag": "@0.12.0",
   "metatest_rev": "@e5aa8e4e19fc4188ac2f6d38368a47d8f07c3df1",
   "mime_rev": "@75890811d4af5af080351ba8a2853ad4c8df98dd",
   "net_nss_rev": "@f81948e9a402db94287a43bb34a07ee0daf56cb5",
   "nss_rev": "@87b96db4268293187d7cf741907a6d5d1d8080e0",
   "oauth2_rev": "@1bff41f4d54505c36f2d1a001b83b8b745c452f5",
   "observe_rev": "@eee2b8ec34236fa46982575fbccff84f61202ac6",
   "observatory_pub_packages_rev": "@45565",
+  "package_config_rev": "@286f9cf48448c4563e735a142c6f9442ab57674e",
   "path_rev": "@93b3e2aa1db0ac0c8bab9d341588d77acda60320",
   "petitparser_rev" : "@37878",
   "ply_rev": "@604b32590ffad5cbb82e4afef1d305512d06ae93",
   "plugin_tag": "@0.1.0",
   "pool_rev": "@22e12aeb16ad0b626900dbe79e4a25391ddfb28c",
   "pub_semver_tag": "@1.2.0",
   "scheduled_test_tag": "@0.11.8+1",
   "shelf_rev": "@1e87b79b21ac5e6fa2f93576d6c06eaa65285ef4",
   "smoke_rev" : "@f3361191cc2a85ebc1e4d4c33aec672d7915aba9",
   "source_maps_rev": "@379b4f31c4e2987eb15934d1ad8b419c6cc897b3",
@@ skipping 124 matching lines @@
   Var("dart_root") + "/third_party/pkg/matcher":
       "https://github.com/dart-lang/matcher.git" + Var("matcher_tag"),
   Var("dart_root") + "/third_party/pkg/metatest":
       "https://github.com/dart-lang/metatest.git" + Var("metatest_rev"),
   Var("dart_root") + "/third_party/pkg/mime":
       "https://github.com/dart-lang/mime.git" + Var("mime_rev"),
   Var("dart_root") + "/third_party/pkg/oauth2":
       "https://github.com/dart-lang/oauth2.git" + Var("oauth2_rev"),
   Var("dart_root") + "/third_party/pkg/observe":
       "https://github.com/dart-lang/observe.git" + Var("observe_rev"),
+  Var("dart_root") + "/third_party/pkg/package_config":
+      "https://github.com/dart-lang/package_config.git" +
+      Var("package_config_rev"),
   Var("dart_root") + "/third_party/pkg/path":
       "https://github.com/dart-lang/path.git" + Var("path_rev"),
   Var("dart_root") + "/third_party/pkg/plugin":
       "https://github.com/dart-lang/plugin.git" + Var("plugin_tag"),
   Var("dart_root") + "/third_party/pkg/pool":
       "https://github.com/dart-lang/pool.git" + Var("pool_rev"),
   Var("dart_root") + "/third_party/pkg/pub_semver":
       "https://github.com/dart-lang/pub_semver.git" + Var("pub_semver_tag"),
   Var("dart_root") + "/third_party/pkg/scheduled_test":
       "https://github.com/dart-lang/scheduled_test.git" +
@@ skipping 83 matching lines @@
       '--no_auth',
       '--no_resume',
       '--bucket',
       'dart-dependencies',
       '-d',
       '-r',
       Var('dart_root') + '/tools/testing/bin',
     ],
   },
 ]