[extension SW]: Support event listener registration and event dispatching.

chrome/common/extensions/api/_api_features.json

 // Copyright 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 chrome/common/extensions/api/_features.md to understand this file, as
 // well as feature.h, simple_feature.h, and 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 349 matching lines @@
   "experimental.devtools.console": {
     "dependencies": ["permission:experimental", "manifest:devtools_page"],
     "contexts": ["blessed_extension"]
   },
   "extension": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"],
     "contexts": ["blessed_extension"]
   },
   "extension.getURL": {
-    "contexts": ["blessed_extension", "unblessed_extension", "content_script"]
+    "contexts": ["blessed_extension", "unblessed_extension", "content_script", "extension_service_worker"]
   },
   "extension.getViews": [
     {
       "channel": "stable",
       "contexts": ["blessed_extension"],
       "extension_types": ["extension", "legacy_packaged_app"]
     },
     {
       // TODO(yoz): Eliminate this usage.
       "channel": "stable",
@@ skipping 430 matching lines @@
     "dependencies": ["api:tabs"],
     "contexts": ["blessed_extension"]
   }, {
     "channel": "stable",
     "contexts": ["webui"],
     "matches": [
       "chrome://bookmarks/*"
     ]
   }]
 }