Move Declarative Web Request API out of experimental and make it a feature

chrome/common/extensions/api/declarativeWebRequest.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.
 
 [
   {
-    "namespace": "experimental.webRequest",
+    "namespace": "declarativeWebRequest",
     "types": [
       {
         "id": "RequestMatcher",
         "type": "object",
         "description": "Matches network events by various criteria.",
         "properties": {
           "url": {
             "$ref": "UrlFilter",
             "description": "Matches if the condition of the UrlFilter are fulfilled for the URL of the request.",
             "optional": true
           },
           "resourceType": {
             "type": "array",
             "optional": true,
             "description": "Matches if the request type of a request is contained in the list. Requests that cannot match any of the types will be filtered out.",
             "items": { "type": "string", "enum": ["main_frame", "sub_frame", "stylesheet", "script", "image", "object", "xmlhttprequest", "other"] }
           },
-          "instanceType": { "type": "string", "enum": ["experimental.webRequest.RequestMatcher"] }
+          "instanceType": { "type": "string", "enum": ["declarativeWebRequest.RequestMatcher"] }
         }
       },
       {
         "id": "CancelRequest",
         "description": "Declarative event action that cancels a network request.",
         "type": "object",
         "properties": {
-          "instanceType": { "type": "string", "enum": ["experimental.webRequest.CancelRequest"] }
+          "instanceType": { "type": "string", "enum": ["declarativeWebRequest.CancelRequest"] }
         }
       },
       {
         "id": "RedirectRequest",
         "description": "Declarative event action that redirects a network request. (TODO: add destination)",
         "type": "object",
         "properties": {
-          "instanceType": { "type": "string", "enum": ["experimental.webRequest.RedirectRequest"] },
+          "instanceType": { "type": "string", "enum": ["declarativeWebRequest.RedirectRequest"] },
           "redirectUrl": { "type": "string", "description": "Destination to where the request is redirected."}
         }
       }
     ],
     "functions": [
     ],
     "events": [
       {
         "name": "onRequest",
         "options": {
           "supportsListeners": false,
           "supportsRules": true,
           "conditions": ["RequestMatcher"],
           "actions": ["CancelRequest", "RedirectRequest"]
         }
       }
     ]
   }
 ]