Implement the private API for quick unlock.

chrome/common/extensions/api/_api_features.json

 // Copyright 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 extension APIs implemented under src/chrome.
 // See extensions/common/features/* to understand this file, in particular
 // feature.h, simple_feature.h, and base_feature_provider.h.
 //
 // Note that specifying "web_page", "blessed_web_page", or "all" as a context
 // type will require manually updating chrome/renderer/resources/dispatcher.cc.
@@ skipping 681 matching lines @@
   },
   "proxy": {
     "dependencies": ["permission:proxy"],
     "contexts": ["blessed_extension"]
   },
   "imageWriterPrivate": {
     "dependencies": ["permission:imageWriterPrivate"],
     "extension_types": ["platform_app"],
     "contexts": ["blessed_extension"]
   },
+  "quickUnlockPrivate": {
+    "channel": "stable",
+    "contexts": ["webui"],
+    "matches": [
+      "chrome://md-settings/*"
+    ]

[Devlin, 2016/06/13 14:50:23]

this should be cros-only, right?  (I think you specify it in the idl, but good
to do so here, too.

[jdufault, 2016/06/20 22:18:25]

Done.

+  },
   "resourcesPrivate": [{
     "dependencies": ["permission:resourcesPrivate"],
     "contexts": ["blessed_extension"]
   }, {
     "channel": "stable",
     "contexts": ["webui"],
     "matches": [
       "chrome://print/*"
     ]
   }],
@@ skipping 129 matching lines @@
     "internal": true,
     "channel": "stable",
     "dependencies": ["permission:webview"],
     "contexts": ["blessed_extension"]
   },
   "windows": {
     "dependencies": ["api:tabs"],
     "contexts": ["blessed_extension"]
   }
 }