--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -9868,17 +9868,17 @@ nsDocument::ForgetImagePreload(nsIURI* a
     if (req) {
       // Make sure to cancel the request so imagelib knows it's gone.
       req->CancelAndForgetObserver(NS_BINDING_ABORTED);
     }
   }
 }
 
 void
-nsDocument::UpdatePossiblyStaleDocumentState()
+nsIDocument::UpdatePossiblyStaleDocumentState()
 {
   if (!mGotDocumentState.HasState(NS_DOCUMENT_STATE_RTL_LOCALE)) {
     if (IsDocumentRightToLeft()) {
       mDocumentState |= NS_DOCUMENT_STATE_RTL_LOCALE;
     }
     mGotDocumentState |= NS_DOCUMENT_STATE_RTL_LOCALE;
   }
   if (!mGotDocumentState.HasState(NS_DOCUMENT_STATE_WINDOW_INACTIVE)) {
@@ -9886,29 +9886,16 @@ nsDocument::UpdatePossiblyStaleDocumentS
     if (shell && shell->GetPresContext() &&
         shell->GetPresContext()->IsTopLevelWindowInactive()) {
       mDocumentState |= NS_DOCUMENT_STATE_WINDOW_INACTIVE;
     }
     mGotDocumentState |= NS_DOCUMENT_STATE_WINDOW_INACTIVE;
   }
 }
 
-EventStates
-nsDocument::ThreadSafeGetDocumentState() const
-{
-  return mDocumentState;
-}
-
-EventStates
-nsDocument::GetDocumentState()
-{
-  UpdatePossiblyStaleDocumentState();
-  return ThreadSafeGetDocumentState();
-}
-
 namespace {
 
 /**
  * Stub for LoadSheet(), since all we want is to get the sheet into
  * the CSSLoader's style cache
  */
 class StubCSSLoaderObserver final : public nsICSSLoaderObserver {
   ~StubCSSLoaderObserver() {}

--- a/dom/base/nsDocument.h
+++ b/dom/base/nsDocument.h
@@ -838,23 +838,16 @@ public:
                             ReferrerPolicy aReferrerPolicy,
                             const nsAString& aIntegrity) override;
 
   virtual nsresult LoadChromeSheetSync(nsIURI* uri, bool isAgentSheet,
                                        RefPtr<mozilla::StyleSheet>* aSheet) override;
 
   virtual nsISupports* GetCurrentContentSink() override;
 
-  virtual mozilla::EventStates GetDocumentState() final;
-  // GetDocumentState() mutates the state due to lazy resolution;
-  // and can't be used during parallel traversal. Use this instead,
-  // and ensure GetDocumentState() has been called first.
-  // This will assert if the state is stale.
-  virtual mozilla::EventStates ThreadSafeGetDocumentState() const final;
-
   // Only BlockOnload should call this!
   void AsyncBlockOnload();
 
   virtual void SetScrollToRef(nsIURI *aDocumentURI) override;
   virtual void ScrollToRef() override;
   virtual void ResetScrolledToRefAlready() override;
   virtual void SetChangeScrollPosWhenScrollingToRef(bool aValue) override;
 
@@ -1177,18 +1170,16 @@ protected:
   // non-null when this document is in fullscreen mode.
   nsWeakPtr mFullscreenRoot;
 
   RefPtr<PrincipalFlashClassifier> mPrincipalFlashClassifier;
   mozilla::dom::FlashClassification mFlashClassification;
   // Do not use this value directly. Call the |IsThirdParty()| method, which
   // caches its result here.
   mozilla::Maybe<bool> mIsThirdParty;
-private:
-  void UpdatePossiblyStaleDocumentState();
 
 public:
   RefPtr<mozilla::EventListenerManager> mListenerManager;
   RefPtr<mozilla::dom::StyleSheetList> mDOMStyleSheets;
   RefPtr<nsDOMStyleSheetSetList> mStyleSheetSetList;
   RefPtr<mozilla::dom::ScriptLoader> mScriptLoader;
   nsDocHeaderData* mHeaderData;
   /* mIdentifierMap works as follows for IDs:
@@ -1265,19 +1256,16 @@ public:
   uint32_t mUpdateNestLevel;
 
   // The application cache that this document is associated with, if
   // any.  This can change during the lifetime of the document.
   nsCOMPtr<nsIApplicationCache> mApplicationCache;
 
   nsCOMPtr<nsIContent> mFirstBaseNodeWithHref;
 
-  mozilla::EventStates mDocumentState;
-  mozilla::EventStates mGotDocumentState;
-
   RefPtr<nsDOMNavigationTiming> mTiming;
 private:
   friend class nsUnblockOnloadEvent;
   // Recomputes the visibility state but doesn't set the new value.
   mozilla::dom::VisibilityState GetVisibilityState() const;
   void NotifyStyleSheetAdded(mozilla::StyleSheet* aSheet, bool aDocumentSheet);
   void NotifyStyleSheetRemoved(mozilla::StyleSheet* aSheet, bool aDocumentSheet);
 

--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -2636,18 +2636,28 @@ public:
   virtual DocumentTheme GetDocumentLWTheme() { return Doc_Theme_None; }
   virtual DocumentTheme ThreadSafeGetDocumentLWTheme() const { return Doc_Theme_None; }
 
   /**
    * Returns the document state.
    * Document state bits have the form NS_DOCUMENT_STATE_* and are declared in
    * nsIDocument.h.
    */
-  virtual mozilla::EventStates GetDocumentState() = 0;
-  virtual mozilla::EventStates ThreadSafeGetDocumentState() const = 0;
+  mozilla::EventStates GetDocumentState() {
+    UpdatePossiblyStaleDocumentState();
+    return ThreadSafeGetDocumentState();
+  }
+
+  // GetDocumentState() mutates the state due to lazy resolution;
+  // and can't be used during parallel traversal. Use this instead,
+  // and ensure GetDocumentState() has been called first.
+  // This will assert if the state is stale.
+  mozilla::EventStates ThreadSafeGetDocumentState() const {
+    return mDocumentState;
+  }
 
   virtual nsISupports* GetCurrentContentSink() = 0;
 
   virtual void SetScrollToRef(nsIURI *aDocumentURI) = 0;
   virtual void ScrollToRef() = 0;
   virtual void ResetScrolledToRefAlready() = 0;
   virtual void SetChangeScrollPosWhenScrollingToRef(bool aValue) = 0;
 
@@ -3258,16 +3268,18 @@ protected:
   }
 
   bool GetChildDocumentUseCounter(mozilla::UseCounter aUseCounter)
   {
     return mChildDocumentUseCounters[aUseCounter];
   }
 
 private:
+  void UpdatePossiblyStaleDocumentState();
+
   mutable std::bitset<eDeprecatedOperationCount> mDeprecationWarnedAbout;
   mutable std::bitset<eDocumentWarningCount> mDocWarningWarnedAbout;
 
   // Lazy-initialization to have mDocGroup initialized in prior to the
   // SelectorCaches.
   // FIXME(emilio): We can use a single cache when all CSSOM methods are
   // implemented for the Servo backend.
   mozilla::UniquePtr<SelectorCache> mServoSelectorCache;
@@ -3417,16 +3429,19 @@ protected:
 
   // container for per-context fonts (downloadable, SVG, etc.)
   RefPtr<mozilla::dom::FontFaceSet> mFontFaceSet;
 
   // Last time this document or a one of its sub-documents was focused.  If
   // focus has never occurred then mLastFocusTime.IsNull() will be true.
   mozilla::TimeStamp mLastFocusTime;
 
+  mozilla::EventStates mDocumentState;
+  mozilla::EventStates mGotDocumentState;
+
   // True if BIDI is enabled.
   bool mBidiEnabled : 1;
   // True if a MathML element has ever been owned by this document.
   bool mMathMLEnabled : 1;
 
   // True if this document is the initial document for a window.  This should
   // basically be true only for documents that exist in newly-opened windows or
   // documents created to satisfy a GetDocument() on a window when there's no