--- a/dom/media/gmp/GMPServiceChild.cpp
+++ b/dom/media/gmp/GMPServiceChild.cpp
@@ -288,16 +288,23 @@ GeckoMediaPluginServiceChild::UpdateGMPC
   // requests waiting on a CDM to download will retry.
   nsCOMPtr<nsIObserverService> obsService = mozilla::services::GetObserverService();
   MOZ_ASSERT(obsService);
   if (obsService) {
     obsService->NotifyObservers(nullptr, "gmp-changed", nullptr);
   }
 }
 
+void
+GeckoMediaPluginServiceChild::BeginShutdown()
+{
+  MOZ_ASSERT(NS_GetCurrentThread() == mGMPThread);
+  mShuttingDownOnGMPThread = true;
+}
+
 NS_IMETHODIMP
 GeckoMediaPluginServiceChild::HasPluginForAPI(const nsACString& aAPI,
                                               nsTArray<nsCString>* aTags,
                                               bool* aHasPlugin)
 {
   StaticMutexAutoLock lock(sGMPCapabilitiesMutex);
   if (!sGMPCapabilities) {
     *aHasPlugin = false;
@@ -369,16 +376,23 @@ GeckoMediaPluginServiceChild::Observe(ns
 }
 
 RefPtr<GeckoMediaPluginServiceChild::GetServiceChildPromise>
 GeckoMediaPluginServiceChild::GetServiceChild()
 {
   MOZ_ASSERT(NS_GetCurrentThread() == mGMPThread);
 
   if (!mServiceChild) {
+    if (mShuttingDownOnGMPThread) {
+      // We have begun shutdown. Don't allow a new connection to the main
+      // process to be instantiated. This also prevents new plugins being
+      // instantiated.
+      return GetServiceChildPromise::CreateAndReject(NS_ERROR_FAILURE,
+                                                     __func__);
+    }
     dom::ContentChild* contentChild = dom::ContentChild::GetSingleton();
     if (!contentChild) {
       return GetServiceChildPromise::CreateAndReject(NS_ERROR_FAILURE, __func__);
     }
     MozPromiseHolder<GetServiceChildPromise>* holder = mGetServiceChildPromises.AppendElement();
     RefPtr<GetServiceChildPromise> promise = holder->Ensure(__func__);
     if (mGetServiceChildPromises.Length() == 1) {
       nsCOMPtr<nsIRunnable> r = WrapRunnable(
@@ -510,10 +524,28 @@ GMPServiceChild::Create(Endpoint<PGMPSer
   NS_ENSURE_SUCCESS(rv, false);
 
   rv = gmpThread->Dispatch(new OpenPGMPServiceChild(Move(serviceChild),
                                                     Move(aGMPService)),
                            NS_DISPATCH_NORMAL);
   return NS_SUCCEEDED(rv);
 }
 
+ipc::IPCResult
+GMPServiceChild::RecvBeginShutdown()
+{
+  RefPtr<GeckoMediaPluginServiceChild> service =
+    GeckoMediaPluginServiceChild::GetSingleton();
+  MOZ_ASSERT(service && service->mServiceChild.get() == this);
+  if (service) {
+    service->BeginShutdown();
+  }
+  return IPC_OK();
+}
+
+bool
+GMPServiceChild::HaveContentParents() const
+{
+  return mContentParents.Count() > 0;
+}
+
 } // namespace gmp
 } // namespace mozilla

--- a/dom/media/gmp/GMPServiceChild.h
+++ b/dom/media/gmp/GMPServiceChild.h
@@ -37,16 +37,18 @@ public:
   NS_DECL_NSIOBSERVER
 
   void SetServiceChild(UniquePtr<GMPServiceChild>&& aServiceChild);
 
   void RemoveGMPContentParent(GMPContentParent* aGMPContentParent);
 
   static void UpdateGMPCapabilities(nsTArray<mozilla::dom::GMPCapabilityData>&& aCapabilities);
 
+  void BeginShutdown();
+
 protected:
   void InitializePlugins(AbstractThread*) override
   {
     // Nothing to do here.
   }
 
   virtual RefPtr<GetGMPContentParentPromise> GetContentParent(
     GMPCrashHelper* aHelper,
@@ -80,16 +82,20 @@ public:
                                                                 ipc::Endpoint<PGMPContentParent>&& endpoint);
 
   void RemoveGMPContentParent(GMPContentParent* aGMPContentParent);
 
   void GetAlreadyBridgedTo(nsTArray<ProcessId>& aAlreadyBridgedTo);
 
   static bool Create(Endpoint<PGMPServiceChild>&& aGMPService);
 
+  ipc::IPCResult RecvBeginShutdown() override;
+
+  bool HaveContentParents() const;
+
 private:
   nsRefPtrHashtable<nsUint64HashKey, GMPContentParent> mContentParents;
 };
 
 } // namespace gmp
 } // namespace mozilla
 
 #endif // GMPServiceChild_h_

--- a/dom/media/gmp/GMPServiceParent.cpp
+++ b/dom/media/gmp/GMPServiceParent.cpp
@@ -463,16 +463,20 @@ GeckoMediaPluginServiceParent::UnloadPlu
   mShuttingDownOnGMPThread = true;
 
   nsTArray<RefPtr<GMPParent>> plugins;
   {
     MutexAutoLock lock(mMutex);
     // Move all plugins references to a local array. This way mMutex won't be
     // locked when calling CloseActive (to avoid inter-locking).
     Swap(plugins, mPlugins);
+
+    for (GMPServiceParent* parent : mServiceParents) {
+      Unused << parent->SendBeginShutdown();
+    }
   }
 
   LOGD(("%s::%s plugins:%" PRIuSIZE, __CLASS__, __FUNCTION__,
         plugins.Length()));
 #ifdef DEBUG
   for (const auto& plugin : plugins) {
     LOGD(("%s::%s plugin: '%s'", __CLASS__, __FUNCTION__,
           plugin->GetDisplayName().get()));

--- a/dom/media/gmp/PGMPService.ipdl
+++ b/dom/media/gmp/PGMPService.ipdl
@@ -31,12 +31,14 @@ parent:
     returns (uint32_t pluginId,
              ProcessId id,
              nsCString displayName,
              Endpoint<PGMPContentParent> endpoint,
              nsresult aResult);
 
   sync GetGMPNodeId(nsString origin, nsString topLevelOrigin, nsString gmpName)
     returns (nsCString id);
+child:
+  async BeginShutdown();
 };
 
 } // namespace gmp
 } // namespace mozilla