Handle error code METHOD_NOT_FOUND_CODE in InspectorServiceWorker.StopAllWorkers()

telemetry/telemetry/internal/backends/chrome_inspector/inspector_serviceworker.py

 # Copyright 2017 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.
 
+from telemetry.internal.backends.chrome_inspector import inspector_websocket
 from telemetry.core import exceptions
 
-
 class InspectorServiceWorker(object):
-  def __init__(self, inspector_websocket, timeout):
-    self._websocket = inspector_websocket
+  def __init__(self, inspector_socket, timeout):
+    self._websocket = inspector_socket
     self._websocket.RegisterDomain('ServiceWorker', self._OnNotification)
     # ServiceWorker.enable RPC must be called before calling any other methods
     # in ServiceWorker domain.
     res = self._websocket.SyncRequest(
         {'method': 'ServiceWorker.enable'}, timeout)
     if 'error' in res:
       raise exceptions.StoryActionError(res['error']['message'])
 
   def _OnNotification(self, msg):
     # TODO: track service worker events
     # (https://chromedevtools.github.io/devtools-protocol/tot/ServiceWorker/)
     pass
 
   def StopAllWorkers(self, timeout):
     res = self._websocket.SyncRequest(
         {'method': 'ServiceWorker.stopAllWorkers'}, timeout)
     if 'error' in res:
+      code = res['error']['code']
+      if code == inspector_websocket.InspectorWebsocket.METHOD_NOT_FOUND_CODE:
+        raise NotImplementedError(
+            'DevTools method ServiceWorker.stopAllWorkers is not supported by '
+            'this browser.')
       raise exceptions.StoryActionError(res['error']['message'])