Add GYP support for packaged manifests

mojo/public/mojo_application_manifest.gypi

Index: mojo/public/mojo_application_manifest.gypi
diff --git a/mojo/public/mojo_application_manifest.gypi b/mojo/public/mojo_application_manifest.gypi
index bda86404707f917e00e39eab0852d10651b0a2b5..9b89abb93fd6fe1957a4161818888616befdf63e 100644
--- a/mojo/public/mojo_application_manifest.gypi
+++ b/mojo/public/mojo_application_manifest.gypi
@@ -8,23 +8,30 @@
       '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)',
+        ],
       }]
     ],
   },