--- a/dom/clients/manager/ClientSource.cpp
+++ b/dom/clients/manager/ClientSource.cpp
@@ -564,20 +564,19 @@ ClientSource::PostMessage(const ClientPo
     // Shutting down. Just don't deliver this message.
     ref = ClientOpPromise::CreateAndReject(NS_ERROR_FAILURE, __func__);
     return ref.forget();
   }
 
   RefPtr<ServiceWorkerRegistrationInfo> reg =
     swm->GetRegistration(principal, source.Scope());
   if (reg) {
-    RefPtr<ServiceWorkerInfo> serviceWorker = reg->GetByID(source.Id());
-    if (serviceWorker) {
-      RefPtr<ServiceWorker> instance =
-        globalObject->GetOrCreateServiceWorker(source);
+    RefPtr<ServiceWorker> instance =
+      globalObject->GetOrCreateServiceWorker(source);
+    if (instance) {
       init.mSource.SetValue().SetAsServiceWorker() = instance;
     }
   }
 
   RefPtr<MessageEvent> event =
     MessageEvent::Constructor(target, NS_LITERAL_STRING("message"), init);
   event->SetTrusted(true);
 

--- a/dom/serviceworkers/ServiceWorkerRegistrationInfo.cpp
+++ b/dom/serviceworkers/ServiceWorkerRegistrationInfo.cpp
@@ -487,34 +487,16 @@ ServiceWorkerRegistrationInfo::GetWaitin
 ServiceWorkerInfo*
 ServiceWorkerRegistrationInfo::GetActive() const
 {
   MOZ_ASSERT(NS_IsMainThread());
   return mActiveWorker;
 }
 
 ServiceWorkerInfo*
-ServiceWorkerRegistrationInfo::GetByID(uint64_t aID) const
-{
-  if (mActiveWorker && mActiveWorker->ID() == aID) {
-    return mActiveWorker;
-  }
-  if (mWaitingWorker && mWaitingWorker->ID() == aID) {
-    return mWaitingWorker;
-  }
-  if (mInstallingWorker && mInstallingWorker->ID() == aID) {
-    return mInstallingWorker;
-  }
-  if (mEvaluatingWorker && mEvaluatingWorker->ID() == aID) {
-    return mEvaluatingWorker;
-  }
-  return nullptr;
-}
-
-ServiceWorkerInfo*
 ServiceWorkerRegistrationInfo::GetByDescriptor(const ServiceWorkerDescriptor& aDescriptor) const
 {
   if (mActiveWorker && mActiveWorker->Descriptor().Matches(aDescriptor)) {
     return mActiveWorker;
   }
   if (mWaitingWorker && mWaitingWorker->Descriptor().Matches(aDescriptor)) {
     return mWaitingWorker;
   }

--- a/dom/serviceworkers/ServiceWorkerRegistrationInfo.h
+++ b/dom/serviceworkers/ServiceWorkerRegistrationInfo.h
@@ -147,19 +147,16 @@ public:
 
   ServiceWorkerInfo*
   GetWaiting() const;
 
   ServiceWorkerInfo*
   GetActive() const;
 
   ServiceWorkerInfo*
-  GetByID(uint64_t aID) const;
-
-  ServiceWorkerInfo*
   GetByDescriptor(const ServiceWorkerDescriptor& aDescriptor) const;
 
   // Set the given worker as the evaluating service worker.  The worker
   // state is not changed.
   void
   SetEvaluating(ServiceWorkerInfo* aServiceWorker);
 
   // Remove an existing evaluating worker, if present.  The worker will