Change the platform app manifest structure.

chrome/common/extensions/docs/samples.json

 {
   "api": {
     "chrome.alarms.clear": "alarms.html#method-clear",
     "chrome.alarms.clearAll": "alarms.html#method-clearAll",
     "chrome.alarms.create": "alarms.html#method-create",
     "chrome.alarms.get": "alarms.html#method-get",
     "chrome.alarms.getAll": "alarms.html#method-getAll",
     "chrome.alarms.onAlarm": "alarms.html#event-onAlarm",
     "chrome.appWindow.create": "appWindow.html#method-create",
     "chrome.bookmarks.create": "bookmarks.html#method-create",
@@ skipping 657 matching lines @@
         "manifest.json",
         "popup.css",
         "popup.html",
         "popup.js"
       ],
       "source_hash": "6e227746c25a1b9765dbd27e3eb0e7403dee2c65",
       "zip_path": "examples/api/browsingData/basic.zip"
     },
     {
       "api_calls": [
-        "chrome.windows.create"
+        "chrome.appWindow.create"
       ],
       "crx_path": null,
       "description": "Add numbers. Now includes subtraction!",
       "features": [
-        "background_page",
-        "experimental",
-        "windows"
+        "appWindow",
+        "experimental"
       ],
       "icon": "icon_128.png",
       "id": "3fb3045783163c0eaaf0d0ce139f254502192a92",
       "name": "Calculator (Platform App)",
       "packaged_app": false,
       "path": "examples/extensions/calculator/",
       "protocols": [],
-      "search_string": "CALCULATOR (PLATFORM APP) ADD NUMBERS. NOW INCLUDES SUBTRACTION! BACKGROUND_PAGE EXPERIMENTAL WINDOWS CHROME.WINDOWS.CREATE",
+      "search_string": "CALCULATOR (PLATFORM APP) ADD NUMBERS. NOW INCLUDES SUBTRACTION! APPWINDOW EXPERIMENTAL CHROME.APPWINDOW.CREATE",
       "source_files": [
         "calculator.html",
         "controller.js",
         "jquery/jquery.min.js",
         "main.js",
         "manifest.json",
         "model.js",
         "style.css",
         "view.js"
       ],
-      "source_hash": "e7718b346a126dd6511553b51056b53732f664cf",
+      "source_hash": "9ffcc4ae67840e1ac102c0dd1922dac92e6bf3f8",
       "zip_path": "examples/extensions/calculator.zip"
     },
     {
       "api_calls": [
         "chrome.webRequest.onBeforeRequest"
       ],
       "crx_path": null,
       "description": "I can't has cheezburger!",
       "features": [
         "background_page",
@@ skipping 2083 matching lines @@
       "source_files": [
         "manifest.json",
         "popup.html",
         "popup.js",
         "sample.css"
       ],
       "source_hash": "8e51dc3a9577065d22ce92f3c838edc5ceaf4e65",
       "zip_path": "examples/api/extension/isAllowedAccess.zip"
     }
   ]
-}
+}