Adds the OCHamcrest library to the iOS build.

ios/chrome/tools/build/ios_generate_forwarding_headers.py

Index: ios/chrome/tools/build/ios_generate_forwarding_headers.py
diff --git a/ios/chrome/tools/build/ios_generate_forwarding_headers.py b/ios/chrome/tools/build/ios_generate_forwarding_headers.py
new file mode 100755
index 0000000000000000000000000000000000000000..24cf1fd33c92ac106a0f3082b4aa34d0c0582d63
--- /dev/null
+++ b/ios/chrome/tools/build/ios_generate_forwarding_headers.py
@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+# Copyright 2016 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 argparse
+import datetime
+import os
+import sys
+
+COPYRIGHT = """// Copyright {0} 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.\n
+""".format(datetime.date.today().year)
+
+def filter_header_files(inputs):
+  return [filename for filename in inputs if filename.endswith('.h')]
+
+def get_output_filename(input_filename, dest_dir):
+  return os.path.join(dest_dir, os.path.basename(input_filename))
+
+def list_outputs(inputs, dest_dir):
+  outputs = []
+  for filename in filter_header_files(inputs):
+    outputs.append(get_output_filename(filename, dest_dir))
+  return ' '.join(outputs)
+
+def generate_headers(inputs, dest_dir):

[baxley, 2016/02/20 01:11:51]

Would it make any sense to rm the dest_dir? I know we don't need to re-create
the file if it is already there, but I'm just wondering if there's a case where
stuff moves around or is removed, and we may want to clean up?

I guess it's not that big of a deal, it shouldn't change too much, or be that
many files.

[rohitrao (ping after 24h), 2016/02/20 01:18:52]

I can't arbitrarily remove dest_dir because then we will regenerate all of the
files every time, making no-op builds impossible.

But it's a good point that headers might move.  We should probably be reading
the contents of each file and making sure they are correct.  I think that can go
in a future CL.

+  for filename in filter_header_files(inputs):
+    forwarding_header = get_output_filename(filename, dest_dir)
+    if not os.path.isfile(forwarding_header):
+      with open(forwarding_header, 'w') as header:
+        header.write(COPYRIGHT)
+        header.write('#import "{0}"\n'.format(filename))
+
+def DoMain(argv):
+  parser = argparse.ArgumentParser(description='Generate forwarding headers.')
+  parser.add_argument('-o', '--list-outputs', action='store_true',
+                      help='List output files and exit.')
+  parser.add_argument('-d', '--dest-dir', type=str, required=True,
+                      help=('Output directory for forwarding headers.'))
+  parser.add_argument('filenames', metavar='filename', type=str, nargs='+',
+                      help='Input filenames.')
+
+  args = parser.parse_args(argv)
+  if args.list_outputs:
+    return list_outputs(args.filenames, args.dest_dir)

[baxley, 2016/02/20 01:11:51]

Does this list get printed?

[rohitrao (ping after 24h), 2016/02/20 01:18:52]

No, it never gets printed anywhere =)  It actually doesn't matter because
pymod_do_main wants it to be returned as a string, but I'll have the script
print the results if you run the script directly.

+  if args.dest_dir:
+    if not os.path.isdir(args.dest_dir):
+      os.makedirs(args.dest_dir)
+    generate_headers(args.filenames, args.dest_dir)
+    return
+  print >>sys.stderr, 'Neither -o nor -d passed, unsure what to do.'
+
+if __name__ == '__main__':
+  DoMain(sys.argv[1:])