Added 'launcher_page' field to extension manifest.json format.

chrome/common/extensions/api/_manifest_features.json

 // Copyright (c) 2012 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.
 
 // This features file defines manifest keys implemented under src/chrome.
 // See extensions/common/features/* to understand this file, in particular
 // feature.h, simple_feature.h, and base_feature_provider.h.
 
 // To add a new whitelisted ID, SHA-1 it and force it to uppercase. In Bash:
 //
@@ skipping 206 matching lines @@
     "extension_types": "all"
   },
   "input_components": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "key": {
     "channel": "stable",
     "extension_types": "all"
   },
+  "launcher_page": {
+    "channel": "stable",
+    "min_manifest_version": 2,
+    "extension_types": ["platform_app"],
+    "whitelist": [
+      "07BD6A765FFC289FF755D7CAB2893A40EC337FEC",  // http://crbug.com/404000
+      "896B85CC7E913E11C34892C1425A093C0701D386",  // http://crbug.com/404000
+      "11A01C82EF355E674E4F9728A801F5C3CB40D83F"   // http://crbug.com/404000
+    ]
+  },
   "manifest_version": {
     "channel": "stable",
     "extension_types": "all"
   },
   "mime_types": {
     "channel": "stable",
     "extension_types": [ "extension", "legacy_packaged_app", "platform_app" ],
     "whitelist": [
       "oickdpebdnfbgkcaoklfcdhjniefkcji",  // browser_tests
       "gbkeegbaiigmenfmjfclcdgdpimamgkj",  // QuickOffice
@@ skipping 156 matching lines @@
   },
   "url_handlers": {
     "channel": "stable",
     "extension_types": ["platform_app"]
   },
   "version": {
     "channel": "stable",
     "extension_types": "all"
   }
 }