Fix unbalanced add/remove task observer

third_party/WebKit/Source/web/WebKit.cpp

 /*
  * Copyright (C) 2009 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 82 matching lines @@
         s_endOfTaskRunner = new EndOfTaskRunner;
         currentThread->addTaskObserver(s_endOfTaskRunner);
     }
 }
 
 void shutdown()
 {
     ThreadState::current()->cleanupMainThread();
 
     // currentThread() is null if we are running on a thread without a message loop.
-    if (Platform::current()->currentThread()) {
-        // We don't need to (cannot) remove s_endOfTaskRunner from the current
-        // message loop, because the message loop is already destructed before
-        // the shutdown() is called.
-        delete s_endOfTaskRunner;
+    if (WebThread* currentThread = Platform::current()->currentThread()) {
+        currentThread->removeTaskObserver(s_endOfTaskRunner);
         s_endOfTaskRunner = nullptr;
     }
 
     modulesInitializer().shutdown();
 
     V8Initializer::shutdownMainThread();
 
     Platform::shutdown();
 }
 
@@ skipping 57 matching lines @@
     WorkerBackingThread::
         MemoryPressureNotificationToWorkerThreadIsolates(level);
 }
 
 void setRAILModeOnWorkerThreadIsolates(v8::RAILMode railMode)
 {
     WorkerBackingThread::setRAILModeOnWorkerThreadIsolates(railMode);
 }
 
 } // namespace blink