Move chrome.usb to //extensions

extensions/common/api/_api_features.json

 // Copyright 2014 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/extensions.
 // 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 28 matching lines @@
   },
   "storage": {
     "dependencies": ["permission:storage"],
     "contexts": ["blessed_extension", "unblessed_extension", "content_script"]
   },
   "test": {
     "internal": true,
     "channel": "stable",
     "extension_types": "all",
     "contexts": ["blessed_extension", "unblessed_extension", "content_script"]
+  },
+  "usb": {
+    "dependencies": ["permission:usb"],
+    "contexts": ["blessed_extension"]
   }
 }