Remove WaitUntilObserver::decrementPendingActivity() from RespondWithObserver::contextDestroyed()

third_party/WebKit/Source/modules/serviceworkers/WaitUntilObserver.h

 // 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.
 
 #ifndef WaitUntilObserver_h
 #define WaitUntilObserver_h
 
 #include "core/dom/ContextLifecycleObserver.h"
 #include "modules/ModulesExport.h"
 #include "modules/serviceworkers/ServiceWorkerGlobalScopeClient.h"
@@ skipping 32 matching lines @@
   void willDispatchEvent();
   void didDispatchEvent(bool errorOccurred);
 
   // Observes the promise and delays calling the continuation until
   // the given promise is resolved or rejected.
   void waitUntil(ScriptState*, ScriptPromise, ExceptionState&);
 
   // These methods can be called when the lifecycle of ExtendableEvent
   // observed by this WaitUntilObserver should be extended by other reason
   // than ExtendableEvent.waitUntil.
+  // Note: There is no need to call decrementPendingActivity() after the context
+  // is being destroyed.
   void incrementPendingActivity();
   void decrementPendingActivity();
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   friend class InternalsServiceWorker;
   class ThenFunction;
 
   WaitUntilObserver(ExecutionContext*, EventType, int eventID);
 
   void reportError(const ScriptValue&);
 
   void consumeWindowInteraction(TimerBase*);
 
   EventType m_type;
   int m_eventID;
   int m_pendingActivity = 0;
   bool m_hasError = false;
   bool m_eventDispatched = false;
   double m_eventDispatchTime = 0;
   Timer<WaitUntilObserver> m_consumeWindowInteractionTimer;
 };
 
 }  // namespace blink
 
 #endif  // WaitUntilObserver_h