Try run for https://codereview.chromium.org/426593007.

chrome/common/extensions/api/_api_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 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 754 matching lines @@
     "channel": "stable",
     // Do not specify extension_types to prevent webstore from being filtered.
     // Technically, webstore is not in apps or extensions, but it is currently
     // displayed on /extensions/webstore and /apps/webstore.
     "contexts": ["blessed_web_page", "web_page"],
     // Any webpage can use the webstore API.
     "matches": ["http://*/*", "https://*/*"]
   },
   "webstorePrivate": {
     "dependencies": ["permission:webstorePrivate"],
+    // NOTE: even though this is only used by the webstore hosted app, which
+    // normally would mean blessed_web_page, component hosted apps are actually
+    // given the blessed_extension denomination. Confusing.
     "contexts": ["blessed_extension"]
   },
   "webViewInternal": [{
     "internal": true,
     "dependencies": ["permission:webview"],
     "contexts": ["blessed_extension"]
   }, {
     // Component extensions can use the webViewInternal API from iframes.
     "location": "component",
     "internal": true,
@@ skipping 13 matching lines @@
     "internal": true,
     "channel": "stable",
     "dependencies": ["permission:webview"],
     "contexts": ["blessed_extension"]
   },
   "windows": {
     "dependencies": ["api:tabs"],
     "contexts": ["blessed_extension"]
   }
 }