Refactoring unpack_lib_posix and obj_int_extract.

unpack_lib_posix.gypi

+# 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.
+
+# This action takes an archive (.a) file and unpacks it unto object (.o) files.
+# The following input gyp variables are required:
+#   unpack_lib_output_dir, the output directory of extracted object file
+#   unpack_lib_name, the object file to be extracted.
+#   unpack_lib_search_path_list, a list of paths to search for the library.
+#   it must be ['-a', 'path_name1', '-a', 'path_name2'...]
+#
+# For example:
+#   'variables': {
+#     'unpack_lib_search_path_list': [
+#       '-a', '/a/lib.a',
+#       '-a', 'b/lib.a',
+#     ],
+#     'unpack_lib_output_dir':'ouput',
+#     'unpack_lib_name':'offsets.o'
+#   },
+#   'includes': ['unpack_lib_posix.gypi'],
+#
+# It unpacks the first existing library in 'unpack_lib_search_path_list', and
+# extracts 'offsets.o' to 'output' directory.
+
+{
+  'actions': [
+    {
+      'action_name': 'unpack_lib_posix',
+      'inputs': [
+        'unpack_lib_posix.sh',
+      ],
+      'outputs': [
+        '<(unpack_lib_output_dir)/<(unpack_lib_name)',
+      ],
+      'action': [
+        '<(DEPTH)/third_party/libvpx/unpack_lib_posix.sh',
+        '-d', '<(unpack_lib_output_dir)',
+        '-f', '<(unpack_lib_name)',
+        '<@(unpack_lib_search_path_list)',
+      ],
+      'process_output_as_sources': 1,
+    },
+  ],
+}