| Index: Source/core/page/PageLifecycleNotifier.h
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| diff --git a/Source/core/page/PageLifecycleNotifier.h b/Source/core/page/PageLifecycleNotifier.h
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| index 9c28c6731e14b984b42aea76ae3cb3e00dcde310..1cd9fb8dc05668fe5344eba5ed192eb11a1ce7e7 100644
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| --- a/Source/core/page/PageLifecycleNotifier.h
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| +++ b/Source/core/page/PageLifecycleNotifier.h
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| @@ -45,11 +45,13 @@ public:
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|      virtual void addObserver(Observer*) override;
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|      virtual void removeObserver(Observer*) override;
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|  
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| +    virtual void trace(Visitor*) override;
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| +
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|  protected:
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|      explicit PageLifecycleNotifier(Page*);
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|  
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|  private:
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| -    using PageObserverSet = HashSet<PageLifecycleObserver*>;
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| +    using PageObserverSet = WillBeHeapHashSet<RawPtrWillBeWeakMember<PageLifecycleObserver>>;
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|      PageObserverSet m_pageObservers;
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|  };
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|  
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| 
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