[Smart Lock] Expose the easy_unlock.proximity_required pref via the chrome.preferencesPrivate API.

chrome/common/extensions/api/_permission_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 permissions for 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.
 
 // To add a new whitelisted ID, SHA-1 it and force it to uppercase. In Bash:
@@ skipping 801 matching lines @@
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "pointerLock": {
     "channel": "stable",
     "extension_types": ["platform_app"]
   },
   "plugin": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
-  "preferencesPrivate": {
-    "channel": "stable",
-    "extension_types": [
-      "extension"
-    ],
-    "whitelist": [
-      "C41AD9DCD670210295614257EF8C9945AD68D86E",  // Google Now
-      "D5736E4B5CF695CB93A2FB57E4FDC6E5AFAB6FE2",  // http://crbug.com/312900
-      "D57DE394F36DC1C3220E7604C575D29C51A6C495",  // http://crbug.com/319444
-      "3F65507A3B39259B38C8173C6FFA3D12DF64CCE9",  // http://crbug.com/371562
-      "852290F2442EEE45EF673B8DA6090112079012A2"   // http://crbug.com/375484
-    ]
-  },
+  "preferencesPrivate": [
+    {
+      "channel": "stable",
+      "extension_types": [
+        "extension"
+      ],
+      "whitelist": [
+        "C41AD9DCD670210295614257EF8C9945AD68D86E",  // Google Now
+        "D5736E4B5CF695CB93A2FB57E4FDC6E5AFAB6FE2",  // http://crbug.com/312900
+        "D57DE394F36DC1C3220E7604C575D29C51A6C495",  // http://crbug.com/319444
+        "3F65507A3B39259B38C8173C6FFA3D12DF64CCE9",  // http://crbug.com/371562
+        "852290F2442EEE45EF673B8DA6090112079012A2"   // http://crbug.com/375484
+      ]
+    },
+    {
+      "channel": "stable",
+      "extension_types": ["platform_app"],
+      "location": "component"
+    }
+  ],
   "principalsPrivate": {
     "channel": "stable",
     "extension_types": ["extension"],
     "whitelist": [
       "2779FA8B45841D61A37207CCFAC9CB393964FE5B"  // Login Proxy (prototype)
     ]
   },
   "privacy": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
@@ skipping 206 matching lines @@
   "webstorePrivate": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app", "hosted_app"],
     "whitelist": [
       "B44D08FD98F1523ED5837D78D0A606EA9D6206E5",  // Web Store
       "2653F6F6C39BC6EEBD36A09AFB92A19782FF7EB4",  // Enterprise Web Store
       "2779FA8B45841D61A37207CCFAC9CB393964FE5B"   // Login Proxy (prototype)
     ]
   }
 }