Provide script/gypi support for manifest generation

chrome/browser/resources/chromeos/chromevox/merge_manifests.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.
+
+# Given a base manifest, and an override manifest, produces a merged manifest.
+# The merge operation preserves all key values in base except when also
+# specified in override.
+# For that case, override values replace base (preserving nested dictionaries).
+# The following variables must be set before including this file:
+#
+# base_manifest: a valid JSON file path.
+# override_manifest: a valid JSON file path.
+# output_manifest: file path with the resulting manifest.
+
+{
+  'actions': [
+    {
+      'action_name': 'merge_manifests',
+      'message': 'Output merge manifest for <(_target_name)',
+      'inputs': [
+        'tools/merge_manifests.py',
+      ],

[Peter Lundblad, 2014/05/22 00:28:25]

You need to include the manifest files here as well for incremental builds to
work properly.

[David Tseng, 2014/05/22 02:42:04]

Done.

+      'outputs': [
+        '<(output_manifest)'
+      ],
+      'action': [
+        'python',
+        'tools/merge_manifests.py',
+        '<(base_manifest)',
+        '<(override_manifest)',
+        '<(output_manifest)',
+      ],
+    },
+  ],
+}