Add GYP support for packaged manifests

mojo/public/mojo_application_manifest.gypi

 # 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.
 
 {
   'variables': {
     'variables': {
       'application_name%': '<(application_name)',
       'application_type%': '<(application_type)',
       'base_manifest%': 'none',
+      'packaged_manifests%': []
     },
     'application_type%': '<(application_type)',
     'application_name%': '<(application_name)',
     'base_manifest%': '<(base_manifest)',
     'manifest_collator_script%':
         '<(DEPTH)/mojo/public/tools/manifest/manifest_collator.py',
+    'packaged_manifests%': '<(packaged_manifests)',
     'source_manifest%': '<(source_manifest)',
     'conditions': [
       ['application_type=="mojo"', {
-        'output_manifest%': '<(PRODUCT_DIR)/<(application_name)/manifest.json',
+        'output_manifest%': '<(PRODUCT_DIR)/Mojo Applications/<(application_name)/manifest.json',
       }, {
         'output_manifest%': '<(PRODUCT_DIR)/<(application_name)_manifest.json',
       }],
       ['base_manifest!="none"', {
-        'extra_args%': [ '--base-manifest=<(base_manifest)', ],
+        'extra_args%': [
+          '--base-manifest=<(base_manifest)',
+          '<@(packaged_manifests)',
+        ],
       }, {
-        'extra_args%': [],
+        'extra_args%': [
+          '<@(packaged_manifests)',
+        ],
       }]
     ],
   },
   'actions': [{
     'action_name': '<(_target_name)_collation',
     'inputs': [
       '<(manifest_collator_script)',
       '<(source_manifest)',
     ],
     'outputs': [
       '<(output_manifest)',
     ],
     'action': [
       'python',
       '<(manifest_collator_script)',
       '--application-name', '<(application_name)',
       '--parent=<(source_manifest)',
       '--output=<(output_manifest)',
       '<@(extra_args)',
     ],
   }],
 }