Add package_resolver to dartium DEPS, update both DEPS files.

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",
 
   # We use mirrors of all github repos to guarantee reproducibility and
@@ skipping 133 matching lines @@
 
   Var("dart_root") + "/third_party/zlib":
       Var("chromium_git") + "/chromium/src/third_party/zlib.git" +
       Var("zlib_rev"),
 
   Var("dart_root") + "/third_party/boringssl/src":
       "https://boringssl.googlesource.com/boringssl.git" +
       Var("boringssl_rev"),
 
   Var("dart_root") + "/third_party/root_certificates":
-      "https://github.com/dart-lang/root_certificates.git" +
+      (Var("github_mirror") % "root_certificates") +
       Var("root_certificates_rev"),
 
   Var("dart_root") + "/third_party/jinja2":
       Var("chromium_git") + "/chromium/src/third_party/jinja2.git" +
       Var("jinja2_rev"),
 
   Var("dart_root") + "/third_party/ply":
       Var("chromium_git") + "/chromium/src/third_party/ply.git" +
       Var("ply_rev"),
 
@@ skipping 19 matching lines @@
   Var("dart_root") + "/third_party/pkg/boolean_selector":
       (Var("github_dartlang") % "boolean_selector") +
       Var("boolean_selector_tag"),
   Var("dart_root") + "/third_party/pkg/charcode":
       (Var("github_mirror") % "charcode") + Var("charcode_tag"),
   Var("dart_root") + "/third_party/pkg/cli_util":
       (Var("github_mirror") % "cli_util") + Var("cli_util_tag"),
   Var("dart_root") + "/third_party/pkg/collection":
       (Var("github_mirror") % "collection") + Var("collection_tag"),
   Var("dart_root") + "/third_party/pkg/convert":
-      "https://github.com/dart-lang/convert.git" + Var("convert_tag"),
+      (Var("github_mirror") % "convert") + Var("convert_tag"),
   Var("dart_root") + "/third_party/pkg/crypto":
       (Var("github_mirror") % "crypto") + Var("crypto_tag"),
   Var("dart_root") + "/third_party/pkg/csslib":
       (Var("github_mirror") % "csslib") + Var("csslib_tag"),
   Var("dart_root") + "/third_party/pkg/code_transformers":
       (Var("github_dartlang") % "code_transformers") +
       Var("code_transformers_tag"),
   Var("dart_root") + "/third_party/dart-services":
       (Var("github_mirror") % "dart-services") +
       Var("dart_services_rev"),
@@ skipping 78 matching lines @@
       Var("chromium_git")
       + "/external/github.com/google/quiver-dart.git"
       + Var("quiver_tag"),
   Var("dart_root") + "/third_party/pkg/resource":
       (Var("github_mirror") % "resource") + Var("resource_rev"),
   Var("dart_root") + "/third_party/pkg/scheduled_test":
       (Var("github_mirror") % "scheduled_test") + Var("scheduled_test_tag"),
   Var("dart_root") + "/third_party/pkg/shelf":
       (Var("github_mirror") % "shelf") + Var("shelf_tag"),
   Var("dart_root") + "/third_party/pkg/shelf_packages_handler":
-      "https://github.com/dart-lang/shelf_packages_handler.git"
+      (Var("github_mirror") % "shelf_packages_handler")
       + Var("shelf_packages_handler_tag"),
   Var("dart_root") + "/third_party/pkg/shelf_static":
       (Var("github_mirror") % "shelf_static") + Var("shelf_static_tag"),
   Var("dart_root") + "/third_party/pkg/shelf_web_socket":
       (Var("github_mirror") % "shelf_web_socket") +
       Var("shelf_web_socket_tag"),
   Var("dart_root") + "/third_party/pkg/smoke":
       (Var("github_mirror") % "smoke") + Var("smoke_tag"),
   Var("dart_root") + "/third_party/pkg/source_maps":
       (Var("github_mirror") % "source_maps") + Var("source_maps_tag"),
@@ skipping 188 matching lines @@
       "--extract",
       "-s",
       Var('dart_root') + "/third_party/clang.tar.gz.sha1",
     ],
   },
   {
     "pattern": ".",
     "action": ["python", Var("dart_root") + "/tools/gyp_dart.py"],
   },
 ]