--- a/dom/ipc/ProcessHangMonitor.cpp
+++ b/dom/ipc/ProcessHangMonitor.cpp
@@ -241,16 +241,22 @@ public:
    */
   void UpdateMinidump(uint32_t aPluginId, const nsString& aDumpId);
 
   MessageLoop* MonitorLoop() { return mHangMonitor->MonitorLoop(); }
 
 private:
   bool TakeBrowserMinidump(const PluginHangData& aPhd, nsString& aCrashId);
 
+  void SendHangNotification(const HangData& aHangData,
+                            const nsString& aBrowserDumpId,
+                            bool aTakeMinidump);
+
+  void ClearHangNotification();
+
   void DispatchTabChildNotReady(TabId aTabId);
 
   void ForcePaintOnThread(TabId aTabId, uint64_t aLayerObserverEpoch);
 
   void ShutdownOnThread();
 
   const RefPtr<ProcessHangMonitor> mHangMonitor;
 
@@ -696,65 +702,55 @@ void
 HangMonitorParent::Bind(Endpoint<PProcessHangMonitorParent>&& aEndpoint)
 {
   MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());
 
   DebugOnly<bool> ok = aEndpoint.Bind(this);
   MOZ_ASSERT(ok);
 }
 
-class HangObserverNotifier final : public Runnable
+void
+HangMonitorParent::SendHangNotification(const HangData& aHangData,
+                                        const nsString& aBrowserDumpId,
+                                        bool aTakeMinidump)
 {
-public:
-  HangObserverNotifier(HangMonitoredProcess* aProcess,
-                       HangMonitorParent *aParent,
-                       const HangData& aHangData,
-                       const nsString& aBrowserDumpId,
-                       bool aTakeMinidump)
-    : mProcess(aProcess),
-      mParent(aParent),
-      mHangData(aHangData),
-      mBrowserDumpId(aBrowserDumpId),
-      mTakeMinidump(aTakeMinidump)
-  {}
+  // chrome process, main thread
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
 
-  NS_IMETHOD
-  Run() override
-  {
-    // chrome process, main thread
-    MOZ_RELEASE_ASSERT(NS_IsMainThread());
-
-    nsString dumpId;
-    if ((mHangData.type() == HangData::TPluginHangData) && mTakeMinidump) {
-      // We've been handed a partial minidump; complete it with plugin and
-      // content process dumps.
-      const PluginHangData& phd = mHangData.get_PluginHangData();
-      plugins::TakeFullMinidump(phd.pluginId(), phd.contentProcessId(),
-                                mBrowserDumpId, dumpId);
-      mParent->UpdateMinidump(phd.pluginId(), dumpId);
-    } else {
-      // We already have a full minidump; go ahead and use it.
-      dumpId = mBrowserDumpId;
-    }
-
-    mProcess->SetHangData(mHangData, dumpId);
-
-    nsCOMPtr<nsIObserverService> observerService =
-      mozilla::services::GetObserverService();
-    observerService->NotifyObservers(mProcess, "process-hang-report", nullptr);
-    return NS_OK;
+  nsString dumpId;
+  if ((aHangData.type() == HangData::TPluginHangData) && aTakeMinidump) {
+    // We've been handed a partial minidump; complete it with plugin and
+    // content process dumps.
+    const PluginHangData& phd = aHangData.get_PluginHangData();
+    plugins::TakeFullMinidump(phd.pluginId(), phd.contentProcessId(),
+                              aBrowserDumpId, dumpId);
+    UpdateMinidump(phd.pluginId(), dumpId);
+  } else {
+    // We already have a full minidump; go ahead and use it.
+    dumpId = aBrowserDumpId;
   }
 
-private:
-  RefPtr<HangMonitoredProcess> mProcess;
-  HangMonitorParent* mParent;
-  HangData mHangData;
-  nsAutoString mBrowserDumpId;
-  bool mTakeMinidump;
-};
+  mProcess->SetHangData(aHangData, dumpId);
+
+  nsCOMPtr<nsIObserverService> observerService =
+    mozilla::services::GetObserverService();
+  observerService->NotifyObservers(mProcess, "process-hang-report", nullptr);
+}
+
+void
+HangMonitorParent::ClearHangNotification()
+{
+  // chrome process, main thread
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  mProcess->ClearHang();
+
+  nsCOMPtr<nsIObserverService> observerService =
+    mozilla::services::GetObserverService();
+  observerService->NotifyObservers(mProcess, "clear-hang-report", nullptr);
+}
 
 // Take a minidump of the browser process if one wasn't already taken for the
 // plugin that caused the hang. Return false if a dump was already available or
 // true if new one has been taken.
 bool
 HangMonitorParent::TakeBrowserMinidump(const PluginHangData& aPhd,
                                        nsString& aCrashId)
 {
@@ -812,64 +808,41 @@ HangMonitorParent::RecvHangEvidence(cons
   if (aHangData.type() == HangData::TPluginHangData) {
     takeMinidump = TakeBrowserMinidump(aHangData.get_PluginHangData(), crashId);
   }
 
   mHangMonitor->InitiateCPOWTimeout();
 
   MonitorAutoLock lock(mMonitor);
 
-  nsCOMPtr<nsIRunnable> notifier =
-    new HangObserverNotifier(mProcess, this, aHangData, crashId, takeMinidump);
-  NS_DispatchToMainThread(notifier);
+  NS_DispatchToMainThread(
+    mMainThreadTaskFactory.NewRunnableMethod(
+      &HangMonitorParent::SendHangNotification, aHangData, crashId,
+      takeMinidump));
 
   return IPC_OK();
 }
 
-class ClearHangNotifier final : public Runnable
-{
-public:
-  explicit ClearHangNotifier(HangMonitoredProcess* aProcess)
-    : mProcess(aProcess)
-  {}
-
-  NS_IMETHOD
-  Run() override
-  {
-    // chrome process, main thread
-    MOZ_RELEASE_ASSERT(NS_IsMainThread());
-    mProcess->ClearHang();
-
-    nsCOMPtr<nsIObserverService> observerService =
-      mozilla::services::GetObserverService();
-    observerService->NotifyObservers(mProcess, "clear-hang-report", nullptr);
-    return NS_OK;
-  }
-
-private:
-  RefPtr<HangMonitoredProcess> mProcess;
-};
-
 mozilla::ipc::IPCResult
 HangMonitorParent::RecvClearHang()
 {
   // chrome process, background thread
   MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());
 
   if (!mReportHangs) {
     return IPC_OK();
   }
 
   mHangMonitor->InitiateCPOWTimeout();
 
   MonitorAutoLock lock(mMonitor);
 
-  nsCOMPtr<nsIRunnable> notifier =
-    new ClearHangNotifier(mProcess);
-  NS_DispatchToMainThread(notifier);
+  NS_DispatchToMainThread(
+    mMainThreadTaskFactory.NewRunnableMethod(
+      &HangMonitorParent::ClearHangNotification));
 
   return IPC_OK();
 }
 
 void
 HangMonitorParent::TerminateScript()
 {
   MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());