Reland of Clear LifecycleObserver::m_context when LifecycleObserver::contextDestroyed gets called

third_party/WebKit/Source/modules/websockets/DOMWebSocket.cpp

 /*
  * Copyright (C) 2011 Google Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 225 matching lines @@
 {
 }
 
 DOMWebSocket::~DOMWebSocket()
 {
     ASSERT(!m_channel);
 }
 
 void DOMWebSocket::logError(const String& message)
 {
-    getExecutionContext()->addConsoleMessage(ConsoleMessage::create(JSMessageSource, ErrorMessageLevel, message));
+    if (getExecutionContext())
+        getExecutionContext()->addConsoleMessage(ConsoleMessage::create(JSMessageSource, ErrorMessageLevel, message));
 }
 
 DOMWebSocket* DOMWebSocket::create(ExecutionContext* context, const String& url, ExceptionState& exceptionState)
 {
     StringOrStringSequence protocols;
     return create(context, url, protocols, exceptionState);
 }
 
 DOMWebSocket* DOMWebSocket::create(ExecutionContext* context, const String& url, const StringOrStringSequence& protocols, ExceptionState& exceptionState)
 {
@@ skipping 531 matching lines @@
 DEFINE_TRACE(DOMWebSocket)
 {
     visitor->trace(m_channel);
     visitor->trace(m_eventQueue);
     WebSocketChannelClient::trace(visitor);
     EventTargetWithInlineData::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink