Make dart recipes explicitly set GIT_MODE

scripts/slave/recipes/dart/dart_vm.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 DEPS = [
   'depot_tools/bot_update',
   'file',
   'depot_tools/gclient',
   'recipe_engine/path',
   'recipe_engine/platform',
@@ skipping 106 matching lines @@
     'mode': mode,
     'target_arch': 'x64',
     'env': default_envs['linux'],
     'checked': True,
     'test_args': ['--hot-reload-rollback',
                   '--builder-tag=no_ipv6'],
   }
 
 
 def RunSteps(api):
-  api.gclient.set_config('dart')
+  api.gclient.set_config('dart', GIT_MODE=True)
   api.path.c.dynamic_paths['tools'] = None
   api.bot_update.ensure_checkout(force=True)
   api.path['tools'] = api.path['checkout'].join('tools')
   buildername = str(api.properties.get('buildername')) # Convert from unicode.
   (buildername, _, channel) = buildername.rpartition('-')
   assert channel in ['be', 'dev', 'stable', 'integration']
   b = builders[buildername]
 
   if b.get('clobber', False):
       api.python('clobber',
@@ skipping 46 matching lines @@
 
 def GenTests(api):
    yield (
       api.test('vm-linux-release-x64-asan-be') + api.platform('linux', 64) +
       api.properties.generic(mastername='client.dart',
                              buildername='vm-linux-release-x64-asan-be'))
    yield (
       api.test('test-coverage') + api.platform('linux', 32) +
       api.properties.generic(mastername='client.dart',
                              buildername='test-coverage-be'))