Introduce chrome.displaySource API

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 109 matching lines @@
   },
   "declarativeWebRequest": {
     "dependencies": ["permission:declarativeWebRequest"],
     "contexts": ["blessed_extension"]
   },
   "diagnostics": {
     "dependencies": ["permission:diagnostics"],
     "extension_types": ["platform_app"],
     "contexts": ["blessed_extension"]
   },
+  "displaySource": {
+    "dependencies": ["permission:displaySource"],
+    "contexts": ["blessed_extension"]
+  },
   "dns": {
     "dependencies": ["permission:dns"],
     "contexts": ["blessed_extension"]
   },
   "documentScan": {
     "dependencies": ["permission:documentScan"],
     "contexts": ["blessed_extension"]
   },
   // This is not a real API, only here for documentation purposes.
   // See http://crbug.com/275944 for background.
@@ skipping 320 matching lines @@
   }, {
     "channel": "stable",
     "contexts": ["webui"],
     "matches": [
       "chrome://chrome-signin/*",
       "chrome://media-router/*",
       "chrome://oobe/*"
     ]
   }]
 }