--- a/dom/media/systemservices/CamerasChild.cpp
+++ b/dom/media/systemservices/CamerasChild.cpp
@@ -1,16 +1,15 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set sw=2 ts=8 et ft=cpp : */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "CamerasChild.h"
-#include "CamerasUtils.h"
 
 #include "webrtc/video_engine/include/vie_capture.h"
 #undef FF
 
 #include "mozilla/Assertions.h"
 #include "mozilla/ipc/BackgroundChild.h"
 #include "mozilla/ipc/PBackgroundChild.h"
 #include "mozilla/Logging.h"
@@ -482,24 +481,24 @@ Shutdown(void)
     return;
   }
   child->ShutdownAll();
 }
 
 class ShutdownRunnable : public Runnable {
 public:
   explicit
-  ShutdownRunnable(RefPtr<Runnable> aReplyEvent)
+  ShutdownRunnable(already_AddRefed<Runnable>&& aReplyEvent)
     : mReplyEvent(aReplyEvent) {};
 
   NS_IMETHOD Run() override {
     LOG(("Closing BackgroundChild"));
     ipc::BackgroundChild::CloseForCurrentThread();
 
-    NS_DispatchToMainThread(mReplyEvent);
+    NS_DispatchToMainThread(mReplyEvent.forget());
 
     return NS_OK;
   }
 
 private:
   RefPtr<Runnable> mReplyEvent;
 };
 
@@ -539,20 +538,20 @@ CamerasChild::ShutdownParent()
 void
 CamerasChild::ShutdownChild()
 {
   // Called with CamerasSingleton::Mutex() held
   if (CamerasSingleton::Thread()) {
     LOG(("PBackground thread exists, dispatching close"));
     // Dispatch closing the IPC thread back to us when the
     // BackgroundChild is closed.
-    RefPtr<Runnable> event =
-      new ThreadDestructor(CamerasSingleton::Thread());
-    RefPtr<ShutdownRunnable> runnable = new ShutdownRunnable(event);
-    CamerasSingleton::Thread()->Dispatch(runnable, NS_DISPATCH_NORMAL);
+    RefPtr<ShutdownRunnable> runnable =
+      new ShutdownRunnable(NewRunnableMethod(CamerasSingleton::Thread(),
+                                             &nsIThread::Shutdown));
+    CamerasSingleton::Thread()->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
   } else {
     LOG(("Shutdown called without PBackground thread"));
   }
   LOG(("Erasing sCameras & thread refs (original thread)"));
   CamerasSingleton::Child() = nullptr;
   CamerasSingleton::Thread() = nullptr;
 }
 

--- a/dom/media/systemservices/CamerasParent.cpp
+++ b/dom/media/systemservices/CamerasParent.cpp
@@ -1,16 +1,15 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set sw=2 ts=8 et ft=cpp : */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "CamerasParent.h"
-#include "CamerasUtils.h"
 #include "MediaEngine.h"
 #include "MediaUtils.h"
 
 #include "mozilla/Assertions.h"
 #include "mozilla/unused.h"
 #include "mozilla/Services.h"
 #include "mozilla/Logging.h"
 #include "mozilla/ipc/BackgroundParent.h"

deleted file mode 100644
--- a/dom/media/systemservices/CamerasUtils.cpp
+++ /dev/null
@@ -1,19 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set sw=2 ts=8 et ft=cpp : */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "mozilla/unused.h"
-#include "nsThreadUtils.h"
-#include "nsCOMPtr.h"
-#include "mozilla/Assertions.h"
-#include "mozilla/ipc/BackgroundChild.h"
-#include "mozilla/ipc/PBackgroundChild.h"
-#include "nsIIPCBackgroundChildCreateCallback.h"
-
-namespace mozilla {
-namespace camera {
-
-}
-}

deleted file mode 100644
--- a/dom/media/systemservices/CamerasUtils.h
+++ /dev/null
@@ -1,43 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set sw=2 ts=8 et ft=cpp : */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef mozilla_CameraUtils_h
-#define mozilla_CameraUtils_h
-
-#include "nsThreadUtils.h"
-#include "nsCOMPtr.h"
-#include "mozilla/UniquePtr.h"
-
-#include "base/thread.h"
-
-namespace mozilla {
-namespace camera {
-
-class ThreadDestructor : public Runnable
-{
-  DISALLOW_COPY_AND_ASSIGN(ThreadDestructor);
-
-public:
-  explicit ThreadDestructor(nsIThread* aThread)
-    : mThread(aThread) {}
-
-  NS_IMETHOD Run() override
-  {
-    if (mThread) {
-      mThread->Shutdown();
-    }
-    return NS_OK;
-  }
-
-private:
-  ~ThreadDestructor() {}
-  nsCOMPtr<nsIThread> mThread;
-};
-
-}
-}
-
-#endif // mozilla_CameraUtils_h

--- a/dom/media/systemservices/moz.build
+++ b/dom/media/systemservices/moz.build
@@ -3,25 +3,23 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 if CONFIG['MOZ_WEBRTC']:
     EXPORTS += [
         'CamerasChild.h',
         'CamerasParent.h',
-        'CamerasUtils.h',
         'LoadManager.h',
         'LoadManagerFactory.h',
         'LoadMonitor.h',
     ]
     UNIFIED_SOURCES += [
         'CamerasChild.cpp',
         'CamerasParent.cpp',
-        'CamerasUtils.cpp',
         'LoadManager.cpp',
         'LoadManagerFactory.cpp',
         'LoadMonitor.cpp',
         'ShmemPool.cpp',
     ]
     LOCAL_INCLUDES += [
         '/media/webrtc/signaling',
         '/media/webrtc/trunk',

--- a/dom/media/webrtc/MediaEngineWebRTC.cpp
+++ b/dom/media/webrtc/MediaEngineWebRTC.cpp
@@ -1,17 +1,16 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set sw=2 ts=8 et ft=cpp : */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "nsIPrefService.h"
 #include "nsIPrefBranch.h"
-#include "CamerasUtils.h"
 
 #include "CSFLog.h"
 #include "prenv.h"
 
 #include "mozilla/Logging.h"
 #ifdef XP_WIN
 #include "mozilla/WindowsVersion.h"
 #endif

--- a/netwerk/base/Tickler.cpp
+++ b/netwerk/base/Tickler.cpp
@@ -28,48 +28,26 @@ Tickler::Tickler()
     , mEnabled(false)
     , mDelay(16)
     , mDuration(TimeDuration::FromMilliseconds(400))
     , mFD(nullptr)
 {
   MOZ_ASSERT(NS_IsMainThread());
 }
 
-class TicklerThreadDestructor  : public Runnable
-{
-public:
-  explicit TicklerThreadDestructor(nsIThread *aThread)
-    : mThread(aThread) { }
-
-  NS_IMETHOD Run() override
-  {
-    MOZ_ASSERT(NS_IsMainThread());
-    if (mThread)
-      mThread->Shutdown();
-    return NS_OK;
-  }
-
-private:
-  ~TicklerThreadDestructor() { }
-  nsCOMPtr<nsIThread> mThread;
-};
-
 Tickler::~Tickler()
 {
   // non main thread uses of the tickler should hold weak
   // references to it if they must hold a reference at all
   MOZ_ASSERT(NS_IsMainThread());
 
-  // Shutting down a thread can spin the event loop - which is a surprising
-  // thing to do from a dtor. Running it on its own event is safer.
-  nsCOMPtr<nsIRunnable> event = new TicklerThreadDestructor(mThread);
-  if (NS_FAILED(NS_DispatchToCurrentThread(event))) {
-    mThread->Shutdown();
+  if (mThread) {
+    mThread->AsyncShutdown();
+    mThread = nullptr;
   }
-  mThread = nullptr;
 
   if (mTimer)
     mTimer->Cancel();
   if (mFD)
     PR_Close(mFD);
 }
 
 nsresult