Update gyp to 6ee91ad8659871916f9aa840d42e1513befdf638

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 13 matching lines @@
   # DO NOT use this var if you don't see a mirror here:
   #   https://chromium.googlesource.com/
   # named like:
   #   external/github.com/dart-lang/NAME
   # It is ok to add a dependency directly on dart-lang (dart-lang only)
   # github repo until the mirror has been created, but please do file a bug
   # against infra to make that happen.
   "github_mirror":
       "https://chromium.googlesource.com/external/github.com/dart-lang/%s.git",
 
-  "gyp_rev": "@1752",
+  "gyp_rev": "@6ee91ad8659871916f9aa840d42e1513befdf638",
   "co19_rev": "@f95f109fea67127a220958794ef5200a63cb454c",
   "chromium_url": "http://src.chromium.org/svn",
   "chromium_git": "https://chromium.googlesource.com",
 
   # Revisions of /third_party/* dependencies.
   "7zip_rev" : "@19997",
   "analyzer_cli_rev" : "@c4e628a8467f75ded563f029dfb2f1738856f471",
   "args_tag": "@0.13.0",
   "async_tag": "@1.2.0",
   "barback_tag" : "@0.15.2+6",
@@ skipping 70 matching lines @@
   "font_awesome_rev": "@31824",
   "barback-0.13.0_rev": "@34853",
   "barback-0.14.0_rev": "@36398",
   "barback-0.14.1_rev": "@38525",
   "source_maps-0.9.4_rev": "@38524",
 }
 
 deps = {
   # Stuff needed for GYP to run.
   Var("dart_root") + "/third_party/gyp":
-      (Var("googlecode_url") % "gyp") + "/trunk" + Var("gyp_rev"),
+      Var('chromium_git') + '/external/gyp.git' + Var("gyp_rev"),
 
   Var("dart_root") + "/tests/co19/src":
       (Var("github_mirror") % "co19") + Var("co19_rev"),
 
   Var("dart_root") + "/third_party/nss":
       Var("chromium_git") + "/chromium/deps/nss.git" + Var("nss_rev"),
 
   Var("dart_root") + "/third_party/sqlite":
       Var("chromium_git") + "/chromium/src/third_party/sqlite.git" +
       Var("sqlite_rev"),
@@ skipping 238 matching lines @@
       '--no_resume',
       '--bucket',
       'dart-dependencies',
       '-d',
       '-r',
       Var('dart_root') + '/third_party/d8',
     ],
   },
 
 ]