Presentation API: ignore page visibility changes if ExecutionContext is destoyed.

Source/modules/presentation/PresentationAvailability.h

 // Copyright 2015 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 PresentationAvailability_h
 #define PresentationAvailability_h
 
 #include "core/dom/ActiveDOMObject.h"
 #include "core/events/EventTarget.h"
 #include "core/page/PageLifecycleObserver.h"
+#include "modules/ModulesExport.h"
 #include "platform/weborigin/KURL.h"
 #include "public/platform/WebURL.h"
 #include "public/platform/modules/presentation/WebPresentationAvailabilityObserver.h"
 
 namespace blink {
 
 class ExecutionContext;
 class ScriptPromiseResolver;
 
 // Expose whether there is a presentation display available for |url|. The
 // object will be initialized with a default value passed via ::take() and will
 // then subscribe to receive callbacks if the status for |url| were to
 // change. The object will only listen to changes when required.
-class PresentationAvailability final
+class MODULES_EXPORT PresentationAvailability final
     : public RefCountedGarbageCollectedEventTargetWithInlineData<PresentationAvailability>
     , public ActiveDOMObject
     , public PageLifecycleObserver
     , public WebPresentationAvailabilityObserver {
     REFCOUNTED_GARBAGE_COLLECTED_EVENT_TARGET(PresentationAvailability);
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(PresentationAvailability);
     DEFINE_WRAPPERTYPEINFO();
 public:
-    // For CallbackPromiseAdapter.
-    using WebType = bool;
-
     static PresentationAvailability* take(ScriptPromiseResolver*, const KURL&, bool);
     ~PresentationAvailability() override;
 
     // EventTarget implementation.
     const AtomicString& interfaceName() const override;
     ExecutionContext* executionContext() const override;
     bool addEventListener(const AtomicString& eventType, PassRefPtrWillBeRawPtr<EventListener>, bool capture) override;
 
     // WebPresentationAvailabilityObserver implementation.
     void availabilityChanged(bool) override;
@@ skipping 31 matching lines @@
     void updateListening();
 
     const KURL m_url;
     bool m_value;
     State m_state;
 };
 
 } // namespace blink
 
 #endif // PresentationAvailability_h