Remove unused which/when packages from 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 105 matching lines @@
   "sunflower_rev": "@879b704933413414679396b129f5dfa96f7a0b1e",
   "test_reflective_loader_tag": "@0.1.0",
   "test_tag": "@0.12.18+1",
   "typed_data_tag": "@1.1.3",
   "usage_tag": "@v3.0.0+1",
   "utf_tag": "@0.9.0+3",
   "watcher_tag": "@0.9.7+3",
   "web_components_rev": "@6349e09f9118dce7ae1b309af5763745e25a9d61",
   "web_socket_channel_tag": "@1.0.4",
   "WebCore_rev": "@3c45690813c112373757bbef53de1602a62af609",
-  "when_tag": "@0.2.0+2",
-  "which_tag": "@0.1.3+1",
   "yaml_tag": "@2.1.12",
   "zlib_rev": "@c3d0a6190f2f8c924a05ab6cc97b8f975bddd33f",
 }
 
 deps = {
   # Stuff needed for GYP to run.
   Var("dart_root") + "/third_party/gyp":
       Var('chromium_git') + '/external/gyp.git' + Var("gyp_rev"),
 
   # Stuff needed for GN build.
@@ skipping 195 matching lines @@
   Var("dart_root") + "/third_party/pkg/utf":
       (Var("github_mirror") % "utf") + Var("utf_tag"),
   Var("dart_root") + "/third_party/pkg/watcher":
       (Var("github_mirror") % "watcher") + Var("watcher_tag"),
   Var("dart_root") + "/third_party/pkg/web_components":
       (Var("github_mirror") % "web-components") +
       Var("web_components_rev"),
   Var("dart_root") + "/third_party/pkg/web_socket_channel":
       (Var("github_mirror") % "web_socket_channel") +
       Var("web_socket_channel_tag"),
-  Var("dart_root") + "/third_party/pkg/when":
-      (Var("github_mirror") % "when") + Var("when_tag"),
-  Var("dart_root") + "/third_party/pkg/which":
-      (Var("github_mirror") % "which") + Var("which_tag"),
   Var("dart_root") + "/third_party/pkg/yaml":
       (Var("github_mirror") % "yaml") + Var("yaml_tag"),
 }
 
 deps_os = {
   "win": {
     Var("dart_root") + "/third_party/cygwin":
       Var("chromium_git") + "/chromium/deps/cygwin.git" +
       "@c89e446b273697fadf3a10ff1007a97c0b7de6df",
   },
@@ skipping 135 matching lines @@
     # Update the Windows toolchain if necessary.
     'name': 'win_toolchain',
     'pattern': '.',
     'action': ['python', 'sdk/build/vs_toolchain.py', 'update'],
   },
   {
     "pattern": ".",
     "action": ["python", Var("dart_root") + "/tools/generate_buildfiles.py"],
   },
 ]