Update pub, making --packages-dir false by default

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 73 matching lines @@
   "observatory_pub_packages_rev": "@26aad88f1c1915d39bbcbff3cad589e2402fdcf1",
   "observe_tag": "@0.13.5",
   "package_config_tag": "@1.0.0",
   "package_resolver_tag": "@1.0.2",
   "path_tag": "@1.3.9",
   "plugin_tag": "@0.2.0",
   "ply_rev": "@604b32590ffad5cbb82e4afef1d305512d06ae93",
   "pool_tag": "@1.2.4",
   "protobuf_tag": "@0.5.3",
   "pub_cache_tag": "@v0.1.0",
-  "pub_rev": "@4ef3e3e8ad8089733d617505cc66fa3d8049b4ae",
+  "pub_rev": "@3dd04bd17ba269ccdd34502a253041dd96ded3be",
   "pub_semver_tag": "@1.3.0",
   "quiver_tag": "@0.22.0",
   "resource_rev":"@a49101ba2deb29c728acba6fb86000a8f730f4b1",
   "root_certificates_rev": "@aed07942ce98507d2be28cbd29e879525410c7fc",
   "scheduled_test_tag": "@0.12.6",
   "shelf_static_tag": "@0.2.4",
   "shelf_packages_handler_tag": "@1.0.0",
   "shelf_tag": "@0.6.5+3",
   "shelf_web_socket_tag": "@0.2.1",
   "smoke_tag" : "@v0.3.6+2",
@@ skipping 468 matching lines @@
     # Pull clang if needed or requested via GYP_DEFINES.
     'name': 'gn_clang',
     'pattern': '.',
     'action': ['python', 'sdk/tools/clang/scripts/update.py', '--if-needed'],
   },
   {
     "pattern": ".",
     "action": ["python", Var("dart_root") + "/tools/gyp_dart.py"],
   },
 ]