Add headers to gn/gni files for all of sky/engine

sky/tools/missing_from_gn

 #!/usr/bin/env python
 # 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.
 
 import subprocess
 import os
 import argparse
 import logging
 
@@ skipping 27 matching lines @@
     logging.info(target)
     sources = map(lambda s: s[2:], gn_desc(target, 'sources'))
     inputs = map(lambda s: s[2:], gn_desc(target, 'inputs'))
     public = map(lambda s: s[2:], gn_desc(target, 'public'))
     script = map(lambda s: s[2:], gn_desc(target, 'script'))
     return sources + inputs + public + script
 
 
 def find_on_disk(path):
     # FIXME: Use os.walk and do fancier ignoring.
-    return stripped_lines_from_command(['find', path, '-type', 'f'])
+    find_cmd = ['find', path, '-type', 'f']
+    return stripped_lines_from_command(find_cmd, cwd=ROOT_DIR)
 
 
 def main():
     logging.basicConfig(level=logging.INFO)
 
     if os.path.exists(GN_CACHE_PATH):
         logging.info('Using cached GN list: %s' % GN_CACHE_PATH)
         in_gn = set(map(str.strip, open(GN_CACHE_PATH).readlines()))
     else:
         logging.info('No gn cache found, rebuilding: %s' % GN_CACHE_PATH)
         in_gn = set(sum(map(used_files, targets_under('//sky')), []))
         open(GN_CACHE_PATH, 'w+').write('\n'.join(in_gn))
 
     on_disk = set(find_on_disk('sky/engine'))
     # Ignore web/tests and bindings/tests
     on_disk = set(filter(lambda p: '/tests/' not in p, on_disk))
 
     missing_from_gn = sorted(on_disk - in_gn)
 
     IGNORED_EXTENSIONS = [
         '.py', # Probably some to remove, probably some to teach gn about.
         # Python files not being known to gn can cause flaky builds too!
         '.pyc',
         '.gypi',
         '.gn',
         '.gni',
-        '.h', # Ignore headers for the moment.
     ]
     for ext in IGNORED_EXTENSIONS:
         missing_from_gn = filter(lambda p: not p.endswith(ext), missing_from_gn)
 
     # All upper-case files like README, DEPS, etc. are fine.
     missing_from_gn = filter(lambda p: not os.path.basename(p).isupper(),
         missing_from_gn)
 
     print '\n'.join(missing_from_gn)
 
 
 if __name__ == '__main__':
     main()