Update DEPS to use new mirrors of dart-lang git repositories.

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 162 matching lines @@
 
   Var("dart_root") + "/third_party/dart-services":
       (Var("github_mirror") % "dart-services") +
       Var("dart_services_rev"),
 
   Var("dart_root") + "/third_party/pkg/analyzer_cli":
       (Var("github_mirror") % "analyzer_cli") + Var("analyzer_cli_rev"),
   Var("dart_root") + "/third_party/pkg/args":
       (Var("github_mirror") % "args") + Var("args_tag"),
   Var("dart_root") + "/third_party/pkg/async":
-      "https://github.com/dart-lang/async.git" + Var("async_tag"),
+      (Var("github_mirror") % "async") + Var("async_tag"),
   Var("dart_root") + "/third_party/pkg/barback":
       (Var("github_mirror") % "barback") + Var("barback_rev"),
   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_rev"),
   Var("dart_root") + "/third_party/pkg/crypto":
       (Var("github_mirror") % "crypto") + Var("crypto_rev"),
@@ skipping 38 matching lines @@
       (Var("github_mirror") % "mime") + Var("mime_rev"),
   Var("dart_root") + "/third_party/pkg/mustache4dart":  
       Var("chromium_git")  
       + "/external/github.com/valotas/mustache4dart.git"   
       + Var("mustache4dart_rev"),
   Var("dart_root") + "/third_party/pkg/oauth2":
       (Var("github_mirror") % "oauth2") + Var("oauth2_rev"),
   Var("dart_root") + "/third_party/pkg/observe":
       (Var("github_mirror") % "observe") + Var("observe_rev"),
   Var("dart_root") + "/third_party/observatory_pub_packages":
-      "https://github.com/dart-lang/observatory_pub_packages.git"
+     (Var("github_mirror") % "observatory_pub_packages") 
       + Var("observatory_pub_packages_rev"),
   Var("dart_root") + "/third_party/pkg/package_config":
       (Var("github_mirror") % "package_config") +
       Var("package_config_tag"),
   Var("dart_root") + "/third_party/pkg/path":
       (Var("github_mirror") % "path") + Var("path_tag"),
   Var("dart_root") + "/third_party/pkg/plugin":
       (Var("github_mirror") % "plugin") + Var("plugin_tag"),
   Var("dart_root") + "/third_party/pkg/pool":
       (Var("github_mirror") % "pool") + Var("pool_rev"),
   Var("dart_root") + "/third_party/pkg/pub_semver":
       (Var("github_mirror") % "pub_semver") + Var("pub_semver_tag"),
   Var("dart_root") + "/third_party/pkg/pub":
-      ("https://github.com/dart-lang/pub.git") + Var("pub_rev"),
+      (Var("github_mirror") % "pub") + Var("pub_rev"),
   Var("dart_root") + "/third_party/pkg/pub_cache":  
       (Var("github_mirror") % "pub_cache") + Var("pub_cache_tag"),
   Var("dart_root") + "/third_party/pkg/quiver": 
       Var("chromium_git")  
       + "/external/github.com/google/quiver-dart.git"  
       + Var("quiver_tag"),
   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_rev"),
   Var("dart_root") + "/third_party/pkg/shelf_static":
       "https://github.com/kevmoo/shelf_static.dart.git" +
       Var("shelf_static_rev"),
   Var("dart_root") + "/third_party/pkg/shelf_web_socket":
       (Var("github_mirror") % "shelf_web_socket") +
       Var("shelf_web_socket_rev"),
   Var("dart_root") + "/third_party/pkg/smoke":
       (Var("github_mirror") % "smoke") + Var("smoke_rev"),
   Var("dart_root") + "/third_party/pkg/source_maps":
       (Var("github_mirror") % "source_maps") + Var("source_maps_tag"),
   Var("dart_root") + "/third_party/pkg/source_span":
       (Var("github_mirror") % "source_span") + Var("source_span_tag"),
   Var("dart_root") + "/third_party/pkg/source_map_stack_trace":
-      "https://github.com/dart-lang/source_map_stack_trace.git" +
+      (Var("github_mirror") % "source_map_stack_trace") +
       Var("source_map_stack_trace_tag"),
   Var("dart_root") + "/third_party/pkg/stack_trace":
       (Var("github_mirror") % "stack_trace") + Var("stack_trace_tag"),
   Var("dart_root") + "/third_party/pkg/string_scanner":
       (Var("github_mirror") % "string_scanner") +
       Var("string_scanner_rev"),
   Var("dart_root") + "/third_party/sunflower":
       (Var("github_mirror") % "sample-sunflower") +
       Var("sunflower_rev"),
   Var("dart_root") + "/third_party/pkg/test":
@@ skipping 82 matching lines @@
       '--no_resume',
       '--bucket',
       'dart-dependencies',
       '-d',
       '-r',
       Var('dart_root') + '/third_party/d8',
     ],
   },
 
 ]