WebUI: Split unpack_pak functionality to its own GN action.

chrome/browser/resources/unpack_pak.py

Index: chrome/browser/resources/unpack_pak.py
diff --git a/chrome/browser/resources/unpack_pak.py b/chrome/browser/resources/unpack_pak.py
index ce6a993f7ed4edcee9bf2c6710e53ec626c0b99c..46692798eeeaa6a14b4f9b75fcc7accde5378312 100755
--- a/chrome/browser/resources/unpack_pak.py
+++ b/chrome/browser/resources/unpack_pak.py
@@ -3,6 +3,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import argparse
 import os
 import re
 import sys
@@ -51,3 +52,16 @@ def unpack(pak_path, out_path):
       os.makedirs(dirname)
     with open(os.path.join(out_path, filename), 'w') as file:
       file.write(text)
+
+
+def main():
+  parser = argparse.ArgumentParser()
+  parser.add_argument('--pak_file')
+  parser.add_argument('--out_folder')
+  args = parser.parse_args()
+
+  unpack(args.pak_file, args.out_folder)
+
+
+if __name__ == '__main__':
+  main()