--- a/dom/workers/RuntimeService.cpp
+++ b/dom/workers/RuntimeService.cpp
@@ -1094,26 +1094,16 @@ public:
     return NS_OK;
   }
 
   virtual void
   PrepareForForgetSkippable() override
   {
   }
 
-  virtual void
-  BeginCycleCollectionCallback() override
-  {
-  }
-
-  virtual void
-  EndCycleCollectionCallback(CycleCollectorResults &aResults) override
-  {
-  }
-
   void
   DispatchDeferredDeletion(bool aContinuation, bool aPurge) override
   {
     MOZ_ASSERT(!aContinuation);
 
     // Do it immediately, no need for asynchronous behavior here.
     nsCycleCollector_doDeferredDeletion();
   }

--- a/js/xpconnect/src/XPCJSContext.cpp
+++ b/js/xpconnect/src/XPCJSContext.cpp
@@ -660,27 +660,29 @@ XPCJSContext::PrepareForForgetSkippable(
     if (obs) {
         obs->NotifyObservers(nullptr, "cycle-collector-forget-skippable", nullptr);
     }
 }
 
 void
 XPCJSContext::BeginCycleCollectionCallback()
 {
+    CycleCollectedJSContext::BeginCycleCollectionCallback();
     nsJSContext::BeginCycleCollectionCallback();
 
     nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
     if (obs) {
         obs->NotifyObservers(nullptr, "cycle-collector-begin", nullptr);
     }
 }
 
 void
 XPCJSContext::EndCycleCollectionCallback(CycleCollectorResults& aResults)
 {
+    CycleCollectedJSContext::EndCycleCollectionCallback(aResults);
     nsJSContext::EndCycleCollectionCallback(aResults);
 
     nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
     if (obs) {
         obs->NotifyObservers(nullptr, "cycle-collector-end", nullptr);
     }
 }
 

--- a/xpcom/base/CycleCollectedJSContext.cpp
+++ b/xpcom/base/CycleCollectedJSContext.cpp
@@ -1324,16 +1324,26 @@ CycleCollectedJSContext::DeferredFinaliz
 
 void
 CycleCollectedJSContext::DumpJSHeap(FILE* aFile)
 {
   js::DumpHeap(Context(), aFile, js::CollectNurseryBeforeDump);
 }
 
 void
+CycleCollectedJSContext::BeginCycleCollectionCallback()
+{
+}
+
+void
+CycleCollectedJSContext::EndCycleCollectionCallback(CycleCollectorResults& aResults)
+{
+}
+
+void
 CycleCollectedJSContext::ProcessStableStateQueue()
 {
   MOZ_ASSERT(mJSContext);
   MOZ_RELEASE_ASSERT(!mDoingStableStates);
   mDoingStableStates = true;
 
   for (uint32_t i = 0; i < mStableStateEvents.Length(); ++i) {
     nsCOMPtr<nsIRunnable> event = mStableStateEvents[i].forget();

--- a/xpcom/base/CycleCollectedJSContext.h
+++ b/xpcom/base/CycleCollectedJSContext.h
@@ -315,18 +315,18 @@ public:
   void DeferredFinalize(DeferredFinalizeAppendFunction aAppendFunc,
                         DeferredFinalizeFunction aFunc,
                         void* aThing);
   void DeferredFinalize(nsISupports* aSupports);
 
   void DumpJSHeap(FILE* aFile);
 
   virtual void PrepareForForgetSkippable() = 0;
-  virtual void BeginCycleCollectionCallback() = 0;
-  virtual void EndCycleCollectionCallback(CycleCollectorResults& aResults) = 0;
+  virtual void BeginCycleCollectionCallback();
+  virtual void EndCycleCollectionCallback(CycleCollectorResults& aResults);
   virtual void DispatchDeferredDeletion(bool aContinuation, bool aPurge = false) = 0;
 
   JSContext* Context() const
   {
     MOZ_ASSERT(mJSContext);
     return mJSContext;
   }