Provide script/gypi support for manifest generation

chrome/browser/resources/chromeos/chromevox/generate_manifest.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.
+
+# Generates an output manifest based on a Jinja2 templated manifest.
+# Include this file inside of your target to generate a manifest.
+# The following variables must be set before including this file:
+#
+# template_manifest_path: a valid Jinja2 file path.
+# output_manifest_path: file path for the resulting manifest.
+#
+# The following variable is optional:
+#
+# is_guest_manifest: 1 or 0; generates a manifest usable while in guest mode.
+
+{
+  'actions': [
+    {
+      'action_name': 'generate_manifest',
+      'message': 'Generate manifest for <(_target_name)',
+      'variables': {
+        'is_guest_manifest%': 0,
+      },
+      'inputs': [
+        'tools/generate_manifest.py',
+        '<(template_manifest_path)',
+      ],
+      'outputs': [
+        '<(output_manifest_path)'
+      ],
+      'action': [
+        'python',
+        'tools/generate_manifest.py',
+        '-o', '<(output_manifest_path)',
+        '-g', '<(is_guest_manifest)',
+        '<(template_manifest_path)'
+      ],
+    },
+  ],
+}