Revert "Stop adhoc cipd client bootstrap."

This reverts commit c6569aab12.

Reason for revert: This caused crbug.com/674363, needs further investigation.

Original change's description:
> Stop adhoc cipd client bootstrap.
> 
> This was used before to get the git installer, but now depot_tools manages its
> own copy of CIPD.
> 
> BUG=673940
> 
> Change-Id: I1077ff7eb27d9ca191dc0092b7cacaaa69c40449
> Reviewed-on: https://chromium-review.googlesource.com/420303
> Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
> Reviewed-by: Aaron Gable <agable@chromium.org>
> Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
> 

TBR=iannucci@chromium.org,agable@chromium.org,vadimsh@chromium.org,dnj@chromium.org,sebmarchand@chromium.org,chromium-reviews@chromium.org
BUG=673940
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I7aa5561ad0df67831987cd8d53a84105d42d9663
Reviewed-on: https://chromium-review.googlesource.com/420320
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>

bootstrap/win/git_bootstrap.py

@@ -17,8 +17,6 @@ ROOT_DIR = os.path.abspath(os.path.join(THIS_DIR, '..', '..'))
 
 DEVNULL = open(os.devnull, 'w')
 
-BAT_EXT = '.bat' if sys.platform.startswith('win') else ''
-
 
 def _check_call(argv, **kwargs):
   """Wrapper for subprocess.check_call that adds logging."""
@@ -45,6 +43,17 @@ def clean_up_old_git_installations(git_directory):
       shutil.rmtree(full_entry, ignore_errors=True)
 
 
+def bootstrap_cipd(cipd_directory, cipd_platform):
+  """Bootstraps CIPD client into |cipd_directory|."""
+  _check_call([
+      sys.executable,
+      os.path.join(ROOT_DIR, 'recipe_modules', 'cipd', 'resources',
+                   'bootstrap.py'),
+      '--platform', cipd_platform,
+      '--dest-directory', cipd_directory
+  ])
+
+
 def cipd_install(args, dest_directory, package, version):
   """Installs CIPD |package| at |version| into |dest_directory|."""
   manifest_file = tempfile.mktemp()
@@ -95,6 +104,9 @@ def need_to_install_git(args, git_directory):
 def install_git(args, git_version, git_directory):
   """Installs |git_version| into |git_directory|."""
   cipd_platform = 'windows-%s' % ('amd64' if args.bits == 64 else '386')
+  if not args.cipd_client:
+    bootstrap_cipd(ROOT_DIR, cipd_platform)
+    args.cipd_client = os.path.join(ROOT_DIR, 'cipd')
   temp_dir = tempfile.mkdtemp()
   try:
     cipd_install(args,
@@ -160,9 +172,7 @@ def main(argv):
   parser = argparse.ArgumentParser()
   parser.add_argument('--bits', type=int, choices=(32,64), default=64,
                       help='Bitness of the client to install.')
-  parser.add_argument('--cipd-client',
+  parser.add_argument('--cipd-client', help='Path to CIPD client binary.')
-                      help='Path to CIPD client binary. default: %(default)s',
-                      default=os.path.join(ROOT_DIR, 'cipd'+BAT_EXT))
   parser.add_argument('--cipd-cache-directory',
                       help='Path to CIPD cache directory.')
   parser.add_argument('--force', action='store_true',