Make WebRTC work with Chromium Git checkouts

WebRTC standalone shares a lot of dependencies and build
tools with Chromium. To make the build work, many of the
paths of a Chromium checkout is now emulated by creating
symlinks to files and directories.

All DEPS entries that previously used Var("chromium_trunk")
to reference a Chromium checkout or From("chromium_deps"..)
to reference the Chromium DEPS file are now removed and
replaced by symlink entries in setup_links.py.

The script also handles cleanup of the legacy
Subversion-based dependencies that's needed for the
transition.

Windows: One Windows-specific important change is that
gclient sync|runhooks must now be run from a shell
with Administrator privileges in order to be able to create
symlinks. This also means that Windows XP is no longer
supported.

To transition a previously created checkout:
Run "python setup_links.py --force" to cleanup the old
SVN-based dependencies that have been synced by gclient sync.
For Buildbots, the --force flag is automatically enabled for
their syncs.

BUG=2863, chromium:339647
TEST=Manual testing on Linux, Mac and Windows.
R=andrew@webrtc.org, iannucci@chromium.org, phoglund@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/18379005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6938 4adac7df-926f-26a2-2b94-8c16560cd09d

sync_chromium.py

@@ -0,0 +1,72 @@
+#!/usr/bin/env python
+# Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+import argparse
+import os
+import subprocess
+import sys
+
+
+ROOT_DIR = os.path.dirname(os.path.abspath(__file__))
+
+
+def get_target_os_list():
+  try:
+    main_gclient = os.path.join(os.path.dirname(ROOT_DIR), '.gclient')
+    config_dict = {}
+    with open(main_gclient, 'rb') as deps_content:
+      exec(deps_content, config_dict)
+    return ','.join(config_dict.get('target_os', []))
+  except Exception as e:
+    print >> sys.stderr, "error while parsing .gclient:", e
+
+
+def main():
+  CR_DIR = os.path.join(ROOT_DIR, 'chromium')
+
+  p = argparse.ArgumentParser()
+  p.add_argument('--target-revision', required=True,
+                 help='The target chromium git revision [REQUIRED]')
+  p.add_argument('--chromium-dir', default=CR_DIR,
+                 help=('The path to the chromium directory to sync '
+                       '(default: %(default)r)'))
+  opts = p.parse_args()
+  opts.chromium_dir = os.path.abspath(opts.chromium_dir)
+
+  # Do a quick check to see if we were successful last time to make runhooks
+  # sooper fast.
+  flag_file = os.path.join(opts.chromium_dir, '.last_sync_chromium')
+  if os.path.exists(flag_file):
+    with open(flag_file, 'r') as f:
+      if f.read() == opts.target_revision:
+        print "Chromium already up to date:", opts.target_revision
+        return 0
+    os.unlink(flag_file)
+
+  env = os.environ.copy()
+  env['GYP_CHROMIUM_NO_ACTION'] = '1'
+  gclient_cmd = 'gclient.bat' if sys.platform.startswith('win') else 'gclient'
+  args = [
+      gclient_cmd, 'sync', '--no-history', '--force', '--revision',
+      'src@'+opts.target_revision]
+  target_os_list = get_target_os_list()
+  if target_os_list:
+    args += ['--deps=' + target_os_list]
+
+  print 'Running "%s" in %s' % (' '.join(args), opts.chromium_dir)
+  ret = subprocess.call(args, cwd=opts.chromium_dir, env=env)
+  if ret == 0:
+    with open(flag_file, 'wb') as f:
+      f.write(opts.target_revision)
+
+  return ret
+
+
+if __name__ == '__main__':
+  sys.exit(main())