Make pdfium recipes explicitly set GIT_MODE

scripts/slave/recipes/pdfium.py

 # Copyright 2014 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/gclient',
   'depot_tools/bot_update',
   'recipe_engine/path',
   'recipe_engine/platform',
   'recipe_engine/properties',
@@ skipping 14 matching lines @@
   'gn': Property(default=True, kind=bool),
   'skip_test': Property(default=False, kind=bool),
   'target_os': Property(default=None, kind=str),
 }
 
 def _CheckoutSteps(api, memory_tool, skia, xfa, v8, target_cpu, clang, gn,
                    target_os):
   assert(gn)
 
   # Checkout pdfium and its dependencies (specified in DEPS) using gclient.
-  api.gclient.set_config('pdfium')
+  api.gclient.set_config('pdfium', GIT_MODE=True)
   if target_os:
     api.gclient.c.target_os = {target_os}
   api.bot_update.ensure_checkout(force=True)
 
   gyp_defines = [
       'pdf_enable_v8=%d' % int(v8),
       'pdf_enable_xfa=%d' % int(xfa),
   ]
 
   if skia:
@@ skipping 346 matching lines @@
 
   yield (
       api.test('android') +
       api.platform('linux', 64) +
       api.properties(mastername='client.pdfium',
                      buildername='android',
                      slavename='test_slave',
                      target_os='android',
                      skip_test=True)
   )