diff --git a/dom/media/gmp/GMPServiceParent.cpp b/dom/media/gmp/GMPServiceParent.cpp
index 0427f50afb6a..92aed2806d22 100644
--- a/dom/media/gmp/GMPServiceParent.cpp
+++ b/dom/media/gmp/GMPServiceParent.cpp
@@ -44,6 +44,8 @@
 #include <limits>
 #include "MediaPrefs.h"
 
+using mozilla::ipc::Transport;
+
 namespace mozilla {
 
 #ifdef LOG
@@ -80,7 +82,8 @@ GeckoMediaPluginServiceParent::GetSingleton()
 
 NS_IMPL_ISUPPORTS_INHERITED(GeckoMediaPluginServiceParent,
                             GeckoMediaPluginService,
-                            mozIGeckoMediaPluginChromeService)
+                            mozIGeckoMediaPluginChromeService,
+                            nsIAsyncShutdownBlocker)
 
 GeckoMediaPluginServiceParent::GeckoMediaPluginServiceParent()
   : mShuttingDown(false)
@@ -91,6 +94,7 @@ GeckoMediaPluginServiceParent::GeckoMediaPluginServiceParent()
   , mWaitingForPluginsSyncShutdown(false)
   , mInitPromiseMonitor("GeckoMediaPluginServiceParent::mInitPromiseMonitor")
   , mLoadPluginsFromDiskComplete(false)
+  , mServiceUserCount(0)
 {
   MOZ_ASSERT(NS_IsMainThread());
   mInitPromise.SetMonitor(&mInitPromiseMonitor);
@@ -1838,6 +1842,61 @@ static bool IsNodeIdValid(GMPParent* aParent) {
   return !aParent->GetNodeId().IsEmpty();
 }
 
+static nsCOMPtr<nsIAsyncShutdownClient>
+GetShutdownBarrier()
+{
+  nsCOMPtr<nsIAsyncShutdownService> svc = services::GetAsyncShutdown();
+  MOZ_RELEASE_ASSERT(svc);
+
+  nsCOMPtr<nsIAsyncShutdownClient> barrier;
+  nsresult rv = svc->GetXpcomWillShutdown(getter_AddRefs(barrier));
+
+  MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
+  MOZ_RELEASE_ASSERT(barrier);
+  return barrier.forget();
+}
+
+NS_IMETHODIMP
+GeckoMediaPluginServiceParent::GetName(nsAString& aName)
+{
+  aName = NS_LITERAL_STRING("GeckoMediaPluginServiceParent: shutdown");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GeckoMediaPluginServiceParent::GetState(nsIPropertyBag**)
+{
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GeckoMediaPluginServiceParent::BlockShutdown(nsIAsyncShutdownClient*)
+{
+  return NS_OK;
+}
+
+void
+GeckoMediaPluginServiceParent::ServiceUserCreated()
+{
+  MOZ_ASSERT(mServiceUserCount >= 0);
+  if (++mServiceUserCount == 1) {
+    nsresult rv = GetShutdownBarrier()->AddBlocker(
+      this, NS_LITERAL_STRING(__FILE__), __LINE__,
+      NS_LITERAL_STRING("GeckoMediaPluginServiceParent shutdown"));
+    MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
+  }
+}
+
+void
+GeckoMediaPluginServiceParent::ServiceUserDestroyed()
+{
+  MOZ_ASSERT(mServiceUserCount > 0);
+  if (--mServiceUserCount == 0) {
+    nsresult rv = GetShutdownBarrier()->RemoveBlocker(this);
+    MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
+  }
+}
+
 void
 GeckoMediaPluginServiceParent::ClearStorage()
 {
@@ -1877,6 +1936,9 @@ GeckoMediaPluginServiceParent::GetById(uint32_t aPluginId)
 
 GMPServiceParent::~GMPServiceParent()
 {
+  NS_DispatchToMainThread(
+    NewRunnableMethod(mService.get(),
+                      &GeckoMediaPluginServiceParent::ServiceUserDestroyed));
 }
 
 bool
@@ -1976,9 +2038,38 @@ private:
   nsAutoPtr<GMPServiceParent> mToDelete;
 };
 
+void GMPServiceParent::CloseTransport(Monitor* aSyncMonitor, bool* aCompleted)
+{
+  MOZ_ASSERT(MessageLoop::current() == XRE_GetIOMessageLoop());
+
+  MonitorAutoLock lock(*aSyncMonitor);
+
+  // This deletes the transport.
+  SetTransport(nullptr);
+
+  *aCompleted = true;
+  lock.NotifyAll();
+}
+
 void
 GMPServiceParent::ActorDestroy(ActorDestroyReason aWhy)
 {
+  Monitor monitor("DeleteGMPServiceParent");
+  bool completed = false;
+
+  // Make sure the IPC channel is closed before destroying mToDelete.
+  MonitorAutoLock lock(monitor);
+  RefPtr<Runnable> task =
+    NewNonOwningRunnableMethod<Monitor*, bool*>(this,
+                                                &GMPServiceParent::CloseTransport,
+                                                &monitor,
+                                                &completed);
+  XRE_GetIOMessageLoop()->PostTask(Move(task.forget()));
+
+  while (!completed) {
+    lock.Wait();
+  }
+
   NS_DispatchToCurrentThread(new DeleteGMPServiceParent(this));
 }
 
@@ -2017,12 +2108,17 @@ GMPServiceParent::Create(Transport* aTransport, ProcessId aOtherPid)
   RefPtr<GeckoMediaPluginServiceParent> gmp =
     GeckoMediaPluginServiceParent::GetSingleton();
 
-  nsAutoPtr<GMPServiceParent> serviceParent(new GMPServiceParent(gmp));
+  if (gmp->mShuttingDown) {
+    // Shutdown is initiated. There is no point creating a new actor.
+    return nullptr;
+  }
 
   nsCOMPtr<nsIThread> gmpThread;
   nsresult rv = gmp->GetThread(getter_AddRefs(gmpThread));
   NS_ENSURE_SUCCESS(rv, nullptr);
 
+  nsAutoPtr<GMPServiceParent> serviceParent(new GMPServiceParent(gmp));
+
   bool ok;
   rv = gmpThread->Dispatch(new OpenPGMPServiceParent(serviceParent,
                                                      aTransport,
diff --git a/dom/media/gmp/GMPServiceParent.h b/dom/media/gmp/GMPServiceParent.h
index aefd26cbf532..3a8d613c37e6 100644
--- a/dom/media/gmp/GMPServiceParent.h
+++ b/dom/media/gmp/GMPServiceParent.h
@@ -12,6 +12,7 @@
 #include "nsClassHashtable.h"
 #include "nsDataHashtable.h"
 #include "mozilla/Atomics.h"
+#include "nsIAsyncShutdown.h"
 #include "nsThreadUtils.h"
 #include "mozilla/MozPromise.h"
 #include "GMPStorage.h"
@@ -25,6 +26,7 @@ class GMPParent;
 
 class GeckoMediaPluginServiceParent final : public GeckoMediaPluginService
                                           , public mozIGeckoMediaPluginChromeService
+                                          , public nsIAsyncShutdownBlocker
 {
 public:
   static already_AddRefed<GeckoMediaPluginServiceParent> GetSingleton();
@@ -33,6 +35,7 @@ public:
   nsresult Init() override;
 
   NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSIASYNCSHUTDOWNBLOCKER
 
   // mozIGeckoMediaPluginService
   NS_IMETHOD GetPluginVersionForAPI(const nsACString& aAPI,
@@ -65,6 +68,10 @@ public:
   nsresult ForgetThisSiteNative(const nsAString& aSite,
                                 const mozilla::OriginAttributesPattern& aPattern);
 
+  // Notifies that some user of this class is created/destroyed.
+  void ServiceUserCreated();
+  void ServiceUserDestroyed();
+
 private:
   friend class GMPServiceParent;
 
@@ -217,6 +224,10 @@ private:
 
   // Hashes nodeId to the hashtable of storage for that nodeId.
   nsRefPtrHashtable<nsCStringHashKey, GMPStorage> mTempGMPStorage;
+
+  // Tracks how many users are running (on the GMP thread). Only when this count
+  // drops to 0 can we safely shut down the thread.
+  MainThreadOnly<int32_t> mServiceUserCount;
 };
 
 nsresult ReadSalt(nsIFile* aPath, nsACString& aOutData);
@@ -230,6 +241,7 @@ public:
   explicit GMPServiceParent(GeckoMediaPluginServiceParent* aService)
     : mService(aService)
   {
+    mService->ServiceUserCreated();
   }
   virtual ~GMPServiceParent();
 
@@ -259,6 +271,8 @@ public:
                      nsresult* aOutRv) override;
 
 private:
+  void CloseTransport(Monitor* aSyncMonitor, bool* aCompleted);
+
   RefPtr<GeckoMediaPluginServiceParent> mService;
 };