[Cronet] add base proguard flags

components/cronet/tools/generate_proguard_file.py

+#!/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 optparse
+import sys
+
+# Combines files in |input_files| as one proguard file and write that to
+# |output_file|
+def GenerateProguardFile(output_file, input_files):
+  try:
+    with open(output_file, "wb") as target:
+      for input_file in input_files:
+        f = open(input_file, "rb")
+        for line in f:
+          target.write(line)

[pauljensen, 2016/08/17 11:04:46]

Any reason we don't use "cat" instead of this python program?

[xunjieli, 2016/08/17 12:50:31]

Python scripts work across platforms. We can certainly use "cat." In case that
we need to do more file processing in the future, it's easier to add in a Python
file? 

[pauljensen, 2016/08/17 13:04:07]

"cat" should work on any platform we build for Android.  Chromium already uses
"cat" in build files.  I don't think we should be reinventing basic shell
commands and it's nice to save having to maintain 33 lines of code.  If we need
more processing in the future I'm not opposed to using python.

[xunjieli, 2016/08/17 17:11:44]

Thanks for the comments! I asked on Chromium-dev
(https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/HYpcKxUzKYg).
It looks like we should keep it as it is (using Python rather than shell script,
and having the file in cronet/tools rather than reusing a script from a
different directory)

Let me know if you have any concern. Otherwise I will keep it as it is. I will
wait for a day or two in case anyone has different opinions in the forums :)

[pauljensen, 2016/08/18 15:46:09]

I understand the GN folks' motivations for not using a shell script, but I still
feel this is duplicated code but it appears the division between other
repositories interferes with deduplication, so I'm fine with leaving it as is.

I should note that there are several python scripts that appear to do
concatenation but AFAIK none are in the Chromium repo itself: 
https://cs.chromium.org/search/?q=concat+file:py$+file:cat%5B%5E/%5D*$

[xunjieli, 2016/09/07 15:33:24]

Acknowledged.

+  except IOError:
+    raise Exception("Proguard file generation failed")
+
+
+def main():
+  parser = optparse.OptionParser()
+  parser.add_option('--output-file',
+          help='Output file for the generated proguard file')
+
+  options, input_files = parser.parse_args()
+  GenerateProguardFile(options.output_file, input_files)
+
+
+if __name__ == '__main__':
+  sys.exit(main())