Moved the contextmenu webview API to stable, and removed the experimental API infrastructure.

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 387 matching lines @@
     "internal": true,
     "channel": "stable",
     "contexts": ["blessed_extension"]
   }, {
     // webview uses webRequestInternal API.
     "channel": "stable",
     "internal": true,
     "contexts": ["webui"],
     "matches": ["chrome://chrome-signin/*", "chrome://oobe/*"]
   }],
-  "webViewExperimentalInternal": [{
-    "internal": true,
-    "channel": "dev",
-    "contexts": ["blessed_extension"],
-    "dependencies": ["permission:webview"]
-  },
-  {
-    "internal": true,
-    "channel": "stable",
-    "contexts": ["blessed_extension"],
-    "dependencies": ["permission:webview"],
-    "whitelist": [
-      "8C3741E3AF0B93B6E8E0DDD499BB0B74839EA578",
-      "E703483CEF33DEC18B4B6DD84B5C776FB9182BDB",
-      "1A26E32DE447A17CBE5E9750CDBA78F58539B39C",
-      "59048028102D7B4C681DBC7BC6CD980C3DC66DA3"
-    ]
-  }],
   "webViewInternal": [{
     "internal": true,
     "dependencies": ["permission:webview"],
     "contexts": ["blessed_extension"]
   }, {
     "internal": true,
     "channel": "dev",
     "contexts": ["webui"],
     "matches": ["chrome://chrome-signin/*", "chrome://oobe/*"]
   }],
   "webViewRequest": [{
     "dependencies": ["permission:webview"],
     "contexts": ["blessed_extension"]
   }, {
     "channel": "stable",
     "contexts": ["webui"],
     "matches": ["chrome://chrome-signin/*", "chrome://oobe/*"]
   }]
 }