Add package:isolate 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",
 
   # We use mirrors of all github repos to guarantee reproducibility and
@@ skipping 50 matching lines @@
   "func_rev": "@8d4aea75c21be2179cb00dc2b94a71414653094e",
   "glob_rev": "@704cf75e4f26b417505c5c611bdaacd8808467dd",
   "html_tag" : "@0.12.1+1",
   "http_multi_server_tag" : "@2.0.0",
   "http_parser_tag" : "@3.0.2",
   "http_tag" : "@0.11.3+3",
   "http_throttle_rev" : "@a81f08be942cdd608883c7b67795c12226abc235",
   "idl_parser_rev": "@7fbe68cab90c38147dee4f48c30ad0d496c17915",
   "initialize_rev": "@595d501a92c3716395ad2d81f9aabdb9f90879b6",
   "intl_tag": "@0.13.0",
+  "isolate_tag": "@0.2.2",
   "jinja2_rev": "@2222b31554f03e62600cd7e383376a7c187967a1",
   "json_rpc_2_tag": "@2.0.0",
   "linter_rev": "@7ca3aab6ca45b988440e425c187993a533fbe27e",
   "logging_rev": "@85d83e002670545e9039ad3985f0018ab640e597",
   "markdown_rev": "@4aaadf3d940bb172e1f6285af4d2b1710d309982",
   "matcher_tag": "@0.12.0",
   "metatest_rev": "@e5aa8e4e19fc4188ac2f6d38368a47d8f07c3df1",
   "mime_rev": "@75890811d4af5af080351ba8a2853ad4c8df98dd",
   "mustache4dart_rev" : "@5724cfd85151e5b6b53ddcd3380daf188fe47f92",
   "oauth2_tag": "@1.0.0",
@@ skipping 134 matching lines @@
       Var("http_multi_server_tag"),
   Var("dart_root") + "/third_party/pkg/http_parser":
       (Var("github_mirror") % "http_parser") + Var("http_parser_tag"),
   Var("dart_root") + "/third_party/pkg/http_throttle":
       (Var("github_mirror") % "http_throttle") +
       Var("http_throttle_rev"),
   Var("dart_root") + "/third_party/pkg/initialize":
       (Var("github_dartlang") % "initialize") + Var("initialize_rev"),
   Var("dart_root") + "/third_party/pkg/intl":
       (Var("github_mirror") % "intl") + Var("intl_tag"),
+  Var("dart_root") + "/third_party/pkg/isolate":
+      (Var("github_dartlang") % "isolate") + Var("isolate_tag"),
   Var("dart_root") + "/third_party/pkg/json_rpc_2":
       (Var("github_mirror") % "json_rpc_2") + Var("json_rpc_2_tag"),
   Var("dart_root") + "/third_party/pkg/linter":
       (Var("github_mirror") % "linter") + Var("linter_rev"),
   Var("dart_root") + "/third_party/pkg/logging":
       (Var("github_mirror") % "logging") + Var("logging_rev"),
   Var("dart_root") + "/third_party/pkg/markdown":
       (Var("github_mirror") % "markdown") + Var("markdown_rev"),
   Var("dart_root") + "/third_party/pkg/matcher":
       (Var("github_mirror") % "matcher") + Var("matcher_tag"),
@@ skipping 239 matching lines @@
       "--extract",
       "-s",
       Var('dart_root') + "/third_party/clang.tar.gz.sha1",
     ],
   },
   {
     "pattern": ".",
     "action": ["python", Var("dart_root") + "/tools/gyp_dart.py"],
   },
 ]