1 files changed, 1500 insertions, 0 deletions
diff --git a/xpcom/threads/nsThread.cpp b/xpcom/threads/nsThread.cpp
new file mode 100644
index 000000000..63bd28ca3
--- /dev/null
+++ b/xpcom/threads/nsThread.cpp
@@ -0,0 +1,1500 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 "nsThread.h"
+
+#include "base/message_loop.h"
+
+// Chromium's logging can sometimes leak through...
+#ifdef LOG
+#undef LOG
+#endif
+
+#include "mozilla/ReentrantMonitor.h"
+#include "nsMemoryPressure.h"
+#include "nsThreadManager.h"
+#include "nsIClassInfoImpl.h"
+#include "nsAutoPtr.h"
+#include "nsCOMPtr.h"
+#include "nsQueryObject.h"
+#include "pratom.h"
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/Logging.h"
+#include "nsIObserverService.h"
+#include "mozilla/HangMonitor.h"
+#include "mozilla/IOInterposer.h"
+#include "mozilla/ipc/MessageChannel.h"
+#include "mozilla/ipc/BackgroundChild.h"
+#include "mozilla/Services.h"
+#include "nsXPCOMPrivate.h"
+#include "mozilla/ChaosMode.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "nsIIdlePeriod.h"
+#include "nsIIncrementalRunnable.h"
+#include "nsThreadSyncDispatch.h"
+#include "LeakRefPtr.h"
+
+#ifdef MOZ_CRASHREPORTER
+#include "nsServiceManagerUtils.h"
+#include "nsICrashReporter.h"
+#include "mozilla/dom/ContentChild.h"
+#endif
+
+#ifdef XP_LINUX
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <sched.h>
+#endif
+
+#define HAVE_UALARM _BSD_SOURCE || (_XOPEN_SOURCE >= 500 ||                 \
+                      _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&           \
+                      !(_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700)
+
+#if defined(XP_LINUX) && !defined(ANDROID) && defined(_GNU_SOURCE)
+#define HAVE_SCHED_SETAFFINITY
+#endif
+
+#ifdef XP_MACOSX
+#include <mach/mach.h>
+#include <mach/thread_policy.h>
+#endif
+
+#ifdef MOZ_CANARY
+# include <unistd.h>
+# include <execinfo.h>
+# include <signal.h>
+# include <fcntl.h>
+# include "nsXULAppAPI.h"
+#endif
+
+#if defined(NS_FUNCTION_TIMER) && defined(_MSC_VER)
+#include "nsTimerImpl.h"
+#include "mozilla/StackWalk.h"
+#endif
+#ifdef NS_FUNCTION_TIMER
+#include "nsCRT.h"
+#endif
+
+#ifdef MOZ_TASK_TRACER
+#include "GeckoTaskTracer.h"
+#include "TracedTaskCommon.h"
+using namespace mozilla::tasktracer;
+#endif
+
+using namespace mozilla;
+
+static LazyLogModule sThreadLog("nsThread");
+#ifdef LOG
+#undef LOG
+#endif
+#define LOG(args) MOZ_LOG(sThreadLog, mozilla::LogLevel::Debug, args)
+
+NS_DECL_CI_INTERFACE_GETTER(nsThread)
+
+//-----------------------------------------------------------------------------
+// Because we do not have our own nsIFactory, we have to implement nsIClassInfo
+// somewhat manually.
+
+class nsThreadClassInfo : public nsIClassInfo
+{
+public:
+  NS_DECL_ISUPPORTS_INHERITED  // no mRefCnt
+  NS_DECL_NSICLASSINFO
+
+  nsThreadClassInfo()
+  {
+  }
+};
+
+NS_IMETHODIMP_(MozExternalRefCountType)
+nsThreadClassInfo::AddRef()
+{
+  return 2;
+}
+NS_IMETHODIMP_(MozExternalRefCountType)
+nsThreadClassInfo::Release()
+{
+  return 1;
+}
+NS_IMPL_QUERY_INTERFACE(nsThreadClassInfo, nsIClassInfo)
+
+NS_IMETHODIMP
+nsThreadClassInfo::GetInterfaces(uint32_t* aCount, nsIID*** aArray)
+{
+  return NS_CI_INTERFACE_GETTER_NAME(nsThread)(aCount, aArray);
+}
+
+NS_IMETHODIMP
+nsThreadClassInfo::GetScriptableHelper(nsIXPCScriptable** aResult)
+{
+  *aResult = nullptr;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadClassInfo::GetContractID(char** aResult)
+{
+  *aResult = nullptr;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadClassInfo::GetClassDescription(char** aResult)
+{
+  *aResult = nullptr;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadClassInfo::GetClassID(nsCID** aResult)
+{
+  *aResult = nullptr;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadClassInfo::GetFlags(uint32_t* aResult)
+{
+  *aResult = THREADSAFE;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadClassInfo::GetClassIDNoAlloc(nsCID* aResult)
+{
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+//-----------------------------------------------------------------------------
+
+NS_IMPL_ADDREF(nsThread)
+NS_IMPL_RELEASE(nsThread)
+NS_INTERFACE_MAP_BEGIN(nsThread)
+  NS_INTERFACE_MAP_ENTRY(nsIThread)
+  NS_INTERFACE_MAP_ENTRY(nsIThreadInternal)
+  NS_INTERFACE_MAP_ENTRY(nsIEventTarget)
+  NS_INTERFACE_MAP_ENTRY(nsISupportsPriority)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIThread)
+  if (aIID.Equals(NS_GET_IID(nsIClassInfo))) {
+    static nsThreadClassInfo sThreadClassInfo;
+    foundInterface = static_cast<nsIClassInfo*>(&sThreadClassInfo);
+  } else
+NS_INTERFACE_MAP_END
+NS_IMPL_CI_INTERFACE_GETTER(nsThread, nsIThread, nsIThreadInternal,
+                            nsIEventTarget, nsISupportsPriority)
+
+//-----------------------------------------------------------------------------
+
+class nsThreadStartupEvent : public Runnable
+{
+public:
+  nsThreadStartupEvent()
+    : mMon("nsThreadStartupEvent.mMon")
+    , mInitialized(false)
+  {
+  }
+
+  // This method does not return until the thread startup object is in the
+  // completion state.
+  void Wait()
+  {
+    ReentrantMonitorAutoEnter mon(mMon);
+    while (!mInitialized) {
+      mon.Wait();
+    }
+  }
+
+  // This method needs to be public to support older compilers (xlC_r on AIX).
+  // It should be called directly as this class type is reference counted.
+  virtual ~nsThreadStartupEvent() {}
+
+private:
+  NS_IMETHOD Run() override
+  {
+    ReentrantMonitorAutoEnter mon(mMon);
+    mInitialized = true;
+    mon.Notify();
+    return NS_OK;
+  }
+
+  ReentrantMonitor mMon;
+  bool mInitialized;
+};
+//-----------------------------------------------------------------------------
+
+namespace {
+class DelayedRunnable : public Runnable,
+                        public nsITimerCallback
+{
+public:
+  DelayedRunnable(already_AddRefed<nsIThread> aTargetThread,
+                  already_AddRefed<nsIRunnable> aRunnable,
+                  uint32_t aDelay)
+    : mTargetThread(aTargetThread),
+      mWrappedRunnable(aRunnable),
+      mDelayedFrom(TimeStamp::NowLoRes()),
+      mDelay(aDelay)
+  { }
+
+  NS_DECL_ISUPPORTS_INHERITED
+
+  nsresult Init()
+  {
+    nsresult rv;
+    mTimer = do_CreateInstance(NS_TIMER_CONTRACTID, &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    MOZ_ASSERT(mTimer);
+    rv = mTimer->SetTarget(mTargetThread);
+
+    NS_ENSURE_SUCCESS(rv, rv);
+    return mTimer->InitWithCallback(this, mDelay, nsITimer::TYPE_ONE_SHOT);
+  }
+
+  nsresult DoRun()
+  {
+    nsCOMPtr<nsIRunnable> r = mWrappedRunnable.forget();
+    return r->Run();
+  }
+
+  NS_IMETHOD Run() override
+  {
+    // Already ran?
+    if (!mWrappedRunnable) {
+      return NS_OK;
+    }
+
+    // Are we too early?
+    if ((TimeStamp::NowLoRes() - mDelayedFrom).ToMilliseconds() < mDelay) {
+      return NS_OK; // Let the nsITimer run us.
+    }
+
+    mTimer->Cancel();
+    return DoRun();
+  }
+
+  NS_IMETHOD Notify(nsITimer* aTimer) override
+  {
+    // If we already ran, the timer should have been canceled.
+    MOZ_ASSERT(mWrappedRunnable);
+    MOZ_ASSERT(aTimer == mTimer);
+
+    return DoRun();
+  }
+
+private:
+  ~DelayedRunnable() {}
+
+  nsCOMPtr<nsIThread> mTargetThread;
+  nsCOMPtr<nsIRunnable> mWrappedRunnable;
+  nsCOMPtr<nsITimer> mTimer;
+  TimeStamp mDelayedFrom;
+  uint32_t mDelay;
+};
+
+NS_IMPL_ISUPPORTS_INHERITED(DelayedRunnable, Runnable, nsITimerCallback)
+
+} // anonymous namespace
+
+//-----------------------------------------------------------------------------
+
+struct nsThreadShutdownContext
+{
+  nsThreadShutdownContext(NotNull<nsThread*> aTerminatingThread,
+                          NotNull<nsThread*> aJoiningThread,
+                          bool      aAwaitingShutdownAck)
+    : mTerminatingThread(aTerminatingThread)
+    , mJoiningThread(aJoiningThread)
+    , mAwaitingShutdownAck(aAwaitingShutdownAck)
+  {
+    MOZ_COUNT_CTOR(nsThreadShutdownContext);
+  }
+  ~nsThreadShutdownContext()
+  {
+    MOZ_COUNT_DTOR(nsThreadShutdownContext);
+  }
+
+  // NB: This will be the last reference.
+  NotNull<RefPtr<nsThread>> mTerminatingThread;
+  NotNull<nsThread*> mJoiningThread;
+  bool mAwaitingShutdownAck;
+};
+
+// This event is responsible for notifying nsThread::Shutdown that it is time
+// to call PR_JoinThread. It implements nsICancelableRunnable so that it can
+// run on a DOM Worker thread (where all events must implement
+// nsICancelableRunnable.)
+class nsThreadShutdownAckEvent : public CancelableRunnable
+{
+public:
+  explicit nsThreadShutdownAckEvent(NotNull<nsThreadShutdownContext*> aCtx)
+    : mShutdownContext(aCtx)
+  {
+  }
+  NS_IMETHOD Run() override
+  {
+    mShutdownContext->mTerminatingThread->ShutdownComplete(mShutdownContext);
+    return NS_OK;
+  }
+  nsresult Cancel() override
+  {
+    return Run();
+  }
+private:
+  virtual ~nsThreadShutdownAckEvent() { }
+
+  NotNull<nsThreadShutdownContext*> mShutdownContext;
+};
+
+// This event is responsible for setting mShutdownContext
+class nsThreadShutdownEvent : public Runnable
+{
+public:
+  nsThreadShutdownEvent(NotNull<nsThread*> aThr,
+                        NotNull<nsThreadShutdownContext*> aCtx)
+    : mThread(aThr)
+    , mShutdownContext(aCtx)
+  {
+  }
+  NS_IMETHOD Run() override
+  {
+    mThread->mShutdownContext = mShutdownContext;
+    MessageLoop::current()->Quit();
+    return NS_OK;
+  }
+private:
+  NotNull<RefPtr<nsThread>> mThread;
+  NotNull<nsThreadShutdownContext*> mShutdownContext;
+};
+
+//-----------------------------------------------------------------------------
+
+static void
+SetThreadAffinity(unsigned int cpu)
+{
+#ifdef HAVE_SCHED_SETAFFINITY
+  cpu_set_t cpus;
+  CPU_ZERO(&cpus);
+  CPU_SET(cpu, &cpus);
+  sched_setaffinity(0, sizeof(cpus), &cpus);
+  // Don't assert sched_setaffinity's return value because it intermittently (?)
+  // fails with EINVAL on Linux x64 try runs.
+#elif defined(XP_MACOSX)
+  // OS X does not provide APIs to pin threads to specific processors, but you
+  // can tag threads as belonging to the same "affinity set" and the OS will try
+  // to run them on the same processor. To run threads on different processors,
+  // tag them as belonging to different affinity sets. Tag 0, the default, means
+  // "no affinity" so let's pretend each CPU has its own tag `cpu+1`.
+  thread_affinity_policy_data_t policy;
+  policy.affinity_tag = cpu + 1;
+  MOZ_ALWAYS_TRUE(thread_policy_set(mach_thread_self(), THREAD_AFFINITY_POLICY,
+                                    &policy.affinity_tag, 1) == KERN_SUCCESS);
+#elif defined(XP_WIN)
+  MOZ_ALWAYS_TRUE(SetThreadIdealProcessor(GetCurrentThread(), cpu) != -1);
+#endif
+}
+
+static void
+SetupCurrentThreadForChaosMode()
+{
+  if (!ChaosMode::isActive(ChaosFeature::ThreadScheduling)) {
+    return;
+  }
+
+#ifdef XP_LINUX
+  // PR_SetThreadPriority doesn't really work since priorities >
+  // PR_PRIORITY_NORMAL can't be set by non-root users. Instead we'll just use
+  // setpriority(2) to set random 'nice values'. In regular Linux this is only
+  // a dynamic adjustment so it still doesn't really do what we want, but tools
+  // like 'rr' can be more aggressive about honoring these values.
+  // Some of these calls may fail due to trying to lower the priority
+  // (e.g. something may have already called setpriority() for this thread).
+  // This makes it hard to have non-main threads with higher priority than the
+  // main thread, but that's hard to fix. Tools like rr can choose to honor the
+  // requested values anyway.
+  // Use just 4 priorities so there's a reasonable chance of any two threads
+  // having equal priority.
+  setpriority(PRIO_PROCESS, 0, ChaosMode::randomUint32LessThan(4));
+#else
+  // We should set the affinity here but NSPR doesn't provide a way to expose it.
+  uint32_t priority = ChaosMode::randomUint32LessThan(PR_PRIORITY_LAST + 1);
+  PR_SetThreadPriority(PR_GetCurrentThread(), PRThreadPriority(priority));
+#endif
+
+  // Force half the threads to CPU 0 so they compete for CPU
+  if (ChaosMode::randomUint32LessThan(2)) {
+    SetThreadAffinity(0);
+  }
+}
+
+/*static*/ void
+nsThread::ThreadFunc(void* aArg)
+{
+  using mozilla::ipc::BackgroundChild;
+
+  nsThread* self = static_cast<nsThread*>(aArg);  // strong reference
+  self->mThread = PR_GetCurrentThread();
+  SetupCurrentThreadForChaosMode();
+
+  // Inform the ThreadManager
+  nsThreadManager::get().RegisterCurrentThread(*self);
+
+  mozilla::IOInterposer::RegisterCurrentThread();
+
+  // Wait for and process startup event
+  nsCOMPtr<nsIRunnable> event;
+  {
+    MutexAutoLock lock(self->mLock);
+    if (!self->mEvents->GetEvent(true, getter_AddRefs(event), lock)) {
+      NS_WARNING("failed waiting for thread startup event");
+      return;
+    }
+  }
+  event->Run();  // unblocks nsThread::Init
+  event = nullptr;
+
+  {
+    // Scope for MessageLoop.
+    nsAutoPtr<MessageLoop> loop(
+      new MessageLoop(MessageLoop::TYPE_MOZILLA_NONMAINTHREAD, self));
+
+    // Now, process incoming events...
+    loop->Run();
+
+    BackgroundChild::CloseForCurrentThread();
+
+    // NB: The main thread does not shut down here!  It shuts down via
+    // nsThreadManager::Shutdown.
+
+    // Do NS_ProcessPendingEvents but with special handling to set
+    // mEventsAreDoomed atomically with the removal of the last event. The key
+    // invariant here is that we will never permit PutEvent to succeed if the
+    // event would be left in the queue after our final call to
+    // NS_ProcessPendingEvents. We also have to keep processing events as long
+    // as we have outstanding mRequestedShutdownContexts.
+    while (true) {
+      // Check and see if we're waiting on any threads.
+      self->WaitForAllAsynchronousShutdowns();
+
+      {
+        MutexAutoLock lock(self->mLock);
+        if (!self->mEvents->HasPendingEvent(lock)) {
+          // No events in the queue, so we will stop now. Don't let any more
+          // events be added, since they won't be processed. It is critical
+          // that no PutEvent can occur between testing that the event queue is
+          // empty and setting mEventsAreDoomed!
+          self->mEventsAreDoomed = true;
+          break;
+        }
+      }
+      NS_ProcessPendingEvents(self);
+    }
+  }
+
+  mozilla::IOInterposer::UnregisterCurrentThread();
+
+  // Inform the threadmanager that this thread is going away
+  nsThreadManager::get().UnregisterCurrentThread(*self);
+
+  // Dispatch shutdown ACK
+  NotNull<nsThreadShutdownContext*> context =
+    WrapNotNull(self->mShutdownContext);
+  MOZ_ASSERT(context->mTerminatingThread == self);
+  event = do_QueryObject(new nsThreadShutdownAckEvent(context));
+  context->mJoiningThread->Dispatch(event, NS_DISPATCH_NORMAL);
+
+  // Release any observer of the thread here.
+  self->SetObserver(nullptr);
+
+#ifdef MOZ_TASK_TRACER
+  FreeTraceInfo();
+#endif
+
+  NS_RELEASE(self);
+}
+
+//-----------------------------------------------------------------------------
+
+#ifdef MOZ_CRASHREPORTER
+// Tell the crash reporter to save a memory report if our heuristics determine
+// that an OOM failure is likely to occur soon.
+// Memory usage will not be checked more than every 30 seconds or saved more
+// than every 3 minutes
+// If |aShouldSave == kForceReport|, a report will be saved regardless of
+// whether the process is low on memory or not. However, it will still not be
+// saved if a report was saved less than 3 minutes ago.
+bool
+nsThread::SaveMemoryReportNearOOM(ShouldSaveMemoryReport aShouldSave)
+{
+  // Keep an eye on memory usage (cheap, ~7ms) somewhat frequently,
+  // but save memory reports (expensive, ~75ms) less frequently.
+  const size_t kLowMemoryCheckSeconds = 30;
+  const size_t kLowMemorySaveSeconds = 3 * 60;
+
+  static TimeStamp nextCheck = TimeStamp::NowLoRes()
+    + TimeDuration::FromSeconds(kLowMemoryCheckSeconds);
+  static bool recentlySavedReport = false; // Keeps track of whether a report
+                                           // was saved last time we checked
+
+  // Are we checking again too soon?
+  TimeStamp now = TimeStamp::NowLoRes();
+  if ((aShouldSave == ShouldSaveMemoryReport::kMaybeReport ||
+      recentlySavedReport) && now < nextCheck) {
+    return false;
+  }
+
+  bool needMemoryReport = (aShouldSave == ShouldSaveMemoryReport::kForceReport);
+#ifdef XP_WIN // XXX implement on other platforms as needed
+  // If the report is forced there is no need to check whether it is necessary
+  if (aShouldSave != ShouldSaveMemoryReport::kForceReport) {
+    const size_t LOWMEM_THRESHOLD_VIRTUAL = 200 * 1024 * 1024;
+    MEMORYSTATUSEX statex;
+    statex.dwLength = sizeof(statex);
+    if (GlobalMemoryStatusEx(&statex)) {
+      if (statex.ullAvailVirtual < LOWMEM_THRESHOLD_VIRTUAL) {
+        needMemoryReport = true;
+      }
+    }
+  }
+#endif
+
+  if (needMemoryReport) {
+    if (XRE_IsContentProcess()) {
+      dom::ContentChild* cc = dom::ContentChild::GetSingleton();
+      if (cc) {
+        cc->SendNotifyLowMemory();
+      }
+    } else {
+      nsCOMPtr<nsICrashReporter> cr =
+        do_GetService("@mozilla.org/toolkit/crash-reporter;1");
+      if (cr) {
+        cr->SaveMemoryReport();
+      }
+    }
+    recentlySavedReport = true;
+    nextCheck = now + TimeDuration::FromSeconds(kLowMemorySaveSeconds);
+  } else {
+    recentlySavedReport = false;
+    nextCheck = now + TimeDuration::FromSeconds(kLowMemoryCheckSeconds);
+  }
+
+  return recentlySavedReport;
+}
+#endif
+
+#ifdef MOZ_CANARY
+int sCanaryOutputFD = -1;
+#endif
+
+nsThread::nsThread(MainThreadFlag aMainThread, uint32_t aStackSize)
+  : mLock("nsThread.mLock")
+  , mScriptObserver(nullptr)
+  , mEvents(WrapNotNull(&mEventsRoot))
+  , mEventsRoot(mLock)
+  , mIdleEventsAvailable(mLock, "[nsThread.mEventsAvailable]")
+  , mIdleEvents(mIdleEventsAvailable, nsEventQueue::eNormalQueue)
+  , mPriority(PRIORITY_NORMAL)
+  , mThread(nullptr)
+  , mNestedEventLoopDepth(0)
+  , mStackSize(aStackSize)
+  , mShutdownContext(nullptr)
+  , mShutdownRequired(false)
+  , mEventsAreDoomed(false)
+  , mIsMainThread(aMainThread)
+  , mCanInvokeJS(false)
+{
+}
+
+nsThread::~nsThread()
+{
+  NS_ASSERTION(mRequestedShutdownContexts.IsEmpty(),
+               "shouldn't be waiting on other threads to shutdown");
+#ifdef DEBUG
+  // We deliberately leak these so they can be tracked by the leak checker.
+  // If you're having nsThreadShutdownContext leaks, you can set:
+  //   XPCOM_MEM_LOG_CLASSES=nsThreadShutdownContext
+  // during a test run and that will at least tell you what thread is
+  // requesting shutdown on another, which can be helpful for diagnosing
+  // the leak.
+  for (size_t i = 0; i < mRequestedShutdownContexts.Length(); ++i) {
+    Unused << mRequestedShutdownContexts[i].forget();
+  }
+#endif
+}
+
+nsresult
+nsThread::Init()
+{
+  // spawn thread and wait until it is fully setup
+  RefPtr<nsThreadStartupEvent> startup = new nsThreadStartupEvent();
+
+  NS_ADDREF_THIS();
+
+  mIdlePeriod = new IdlePeriod();
+
+  mShutdownRequired = true;
+
+  // ThreadFunc is responsible for setting mThread
+  if (!PR_CreateThread(PR_USER_THREAD, ThreadFunc, this,
+                       PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD,
+                       PR_JOINABLE_THREAD, mStackSize)) {
+    NS_RELEASE_THIS();
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  // ThreadFunc will wait for this event to be run before it tries to access
+  // mThread.  By delaying insertion of this event into the queue, we ensure
+  // that mThread is set properly.
+  {
+    MutexAutoLock lock(mLock);
+    mEventsRoot.PutEvent(startup, lock); // retain a reference
+  }
+
+  // Wait for thread to call ThreadManager::SetupCurrentThread, which completes
+  // initialization of ThreadFunc.
+  startup->Wait();
+  return NS_OK;
+}
+
+nsresult
+nsThread::InitCurrentThread()
+{
+  mThread = PR_GetCurrentThread();
+  SetupCurrentThreadForChaosMode();
+
+  mIdlePeriod = new IdlePeriod();
+
+  nsThreadManager::get().RegisterCurrentThread(*this);
+  return NS_OK;
+}
+
+nsresult
+nsThread::PutEvent(nsIRunnable* aEvent, nsNestedEventTarget* aTarget)
+{
+  nsCOMPtr<nsIRunnable> event(aEvent);
+  return PutEvent(event.forget(), aTarget);
+}
+
+nsresult
+nsThread::PutEvent(already_AddRefed<nsIRunnable> aEvent, nsNestedEventTarget* aTarget)
+{
+  // We want to leak the reference when we fail to dispatch it, so that
+  // we won't release the event in a wrong thread.
+  LeakRefPtr<nsIRunnable> event(Move(aEvent));
+  nsCOMPtr<nsIThreadObserver> obs;
+
+  {
+    MutexAutoLock lock(mLock);
+    nsChainedEventQueue* queue = aTarget ? aTarget->mQueue : &mEventsRoot;
+    if (!queue || (queue == &mEventsRoot && mEventsAreDoomed)) {
+      NS_WARNING("An event was posted to a thread that will never run it (rejected)");
+      return NS_ERROR_UNEXPECTED;
+    }
+    queue->PutEvent(event.take(), lock);
+
+    // Make sure to grab the observer before dropping the lock, otherwise the
+    // event that we just placed into the queue could run and eventually delete
+    // this nsThread before the calling thread is scheduled again. We would then
+    // crash while trying to access a dead nsThread.
+    obs = mObserver;
+  }
+
+  if (obs) {
+    obs->OnDispatchedEvent(this);
+  }
+
+  return NS_OK;
+}
+
+nsresult
+nsThread::DispatchInternal(already_AddRefed<nsIRunnable> aEvent, uint32_t aFlags,
+                           nsNestedEventTarget* aTarget)
+{
+  // We want to leak the reference when we fail to dispatch it, so that
+  // we won't release the event in a wrong thread.
+  LeakRefPtr<nsIRunnable> event(Move(aEvent));
+  if (NS_WARN_IF(!event)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  if (gXPCOMThreadsShutDown && MAIN_THREAD != mIsMainThread && !aTarget) {
+    NS_ASSERTION(false, "Failed Dispatch after xpcom-shutdown-threads");
+    return NS_ERROR_ILLEGAL_DURING_SHUTDOWN;
+  }
+
+#ifdef MOZ_TASK_TRACER
+  nsCOMPtr<nsIRunnable> tracedRunnable = CreateTracedRunnable(event.take());
+  (static_cast<TracedRunnable*>(tracedRunnable.get()))->DispatchTask();
+  // XXX tracedRunnable will always leaked when we fail to disptch.
+  event = tracedRunnable.forget();
+#endif
+
+  if (aFlags & DISPATCH_SYNC) {
+    nsThread* thread = nsThreadManager::get().GetCurrentThread();
+    if (NS_WARN_IF(!thread)) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+
+    // XXX we should be able to do something better here... we should
+    //     be able to monitor the slot occupied by this event and use
+    //     that to tell us when the event has been processed.
+
+    RefPtr<nsThreadSyncDispatch> wrapper =
+      new nsThreadSyncDispatch(thread, event.take());
+    nsresult rv = PutEvent(wrapper, aTarget); // hold a ref
+    // Don't wait for the event to finish if we didn't dispatch it...
+    if (NS_FAILED(rv)) {
+      // PutEvent leaked the wrapper runnable object on failure, so we
+      // explicitly release this object once for that. Note that this
+      // object will be released again soon because it exits the scope.
+      wrapper.get()->Release();
+      return rv;
+    }
+
+    // Allows waiting; ensure no locks are held that would deadlock us!
+    while (wrapper->IsPending()) {
+      NS_ProcessNextEvent(thread, true);
+    }
+    return NS_OK;
+  }
+
+  NS_ASSERTION(aFlags == NS_DISPATCH_NORMAL ||
+               aFlags == NS_DISPATCH_AT_END, "unexpected dispatch flags");
+  return PutEvent(event.take(), aTarget);
+}
+
+bool
+nsThread::nsChainedEventQueue::GetEvent(bool aMayWait, nsIRunnable** aEvent,
+                                        mozilla::MutexAutoLock& aProofOfLock)
+{
+  bool retVal = false;
+  do {
+    if (mProcessSecondaryQueueRunnable) {
+      MOZ_ASSERT(mSecondaryQueue->HasPendingEvent(aProofOfLock));
+      retVal = mSecondaryQueue->GetEvent(aMayWait, aEvent, aProofOfLock);
+      MOZ_ASSERT(*aEvent);
+      mProcessSecondaryQueueRunnable = false;
+      return retVal;
+    }
+
+    // We don't want to wait if mSecondaryQueue has some events.
+    bool reallyMayWait =
+      aMayWait && !mSecondaryQueue->HasPendingEvent(aProofOfLock);
+    retVal =
+      mNormalQueue->GetEvent(reallyMayWait, aEvent, aProofOfLock);
+
+    // Let's see if we should next time process an event from the secondary
+    // queue.
+    mProcessSecondaryQueueRunnable =
+      mSecondaryQueue->HasPendingEvent(aProofOfLock);
+
+    if (*aEvent) {
+      // We got an event, return early.
+      return retVal;
+    }
+  } while(aMayWait || mProcessSecondaryQueueRunnable);
+
+  return retVal;
+}
+
+//-----------------------------------------------------------------------------
+// nsIEventTarget
+
+NS_IMETHODIMP
+nsThread::DispatchFromScript(nsIRunnable* aEvent, uint32_t aFlags)
+{
+  nsCOMPtr<nsIRunnable> event(aEvent);
+  return Dispatch(event.forget(), aFlags);
+}
+
+NS_IMETHODIMP
+nsThread::Dispatch(already_AddRefed<nsIRunnable> aEvent, uint32_t aFlags)
+{
+  LOG(("THRD(%p) Dispatch [%p %x]\n", this, /* XXX aEvent */nullptr, aFlags));
+
+  return DispatchInternal(Move(aEvent), aFlags, nullptr);
+}
+
+NS_IMETHODIMP
+nsThread::DelayedDispatch(already_AddRefed<nsIRunnable> aEvent, uint32_t aDelayMs)
+{
+  NS_ENSURE_TRUE(!!aDelayMs, NS_ERROR_UNEXPECTED);
+
+  RefPtr<DelayedRunnable> r = new DelayedRunnable(Move(do_AddRef(this)),
+                                                  Move(aEvent),
+                                                  aDelayMs);
+  nsresult rv = r->Init();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return DispatchInternal(r.forget(), 0, nullptr);
+}
+
+NS_IMETHODIMP
+nsThread::IsOnCurrentThread(bool* aResult)
+{
+  *aResult = (PR_GetCurrentThread() == mThread);
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// nsIThread
+
+NS_IMETHODIMP
+nsThread::GetPRThread(PRThread** aResult)
+{
+  *aResult = mThread;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::GetCanInvokeJS(bool* aResult)
+{
+  *aResult = mCanInvokeJS;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::SetCanInvokeJS(bool aCanInvokeJS)
+{
+  mCanInvokeJS = aCanInvokeJS;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::AsyncShutdown()
+{
+  LOG(("THRD(%p) async shutdown\n", this));
+
+  // XXX If we make this warn, then we hit that warning at xpcom shutdown while
+  //     shutting down a thread in a thread pool.  That happens b/c the thread
+  //     in the thread pool is already shutdown by the thread manager.
+  if (!mThread) {
+    return NS_OK;
+  }
+
+  return !!ShutdownInternal(/* aSync = */ false) ? NS_OK : NS_ERROR_UNEXPECTED;
+}
+
+nsThreadShutdownContext*
+nsThread::ShutdownInternal(bool aSync)
+{
+  MOZ_ASSERT(mThread);
+  MOZ_ASSERT(mThread != PR_GetCurrentThread());
+  if (NS_WARN_IF(mThread == PR_GetCurrentThread())) {
+    return nullptr;
+  }
+
+  // Prevent multiple calls to this method
+  {
+    MutexAutoLock lock(mLock);
+    if (!mShutdownRequired) {
+      return nullptr;
+    }
+    mShutdownRequired = false;
+  }
+
+  NotNull<nsThread*> currentThread =
+    WrapNotNull(nsThreadManager::get().GetCurrentThread());
+
+  nsAutoPtr<nsThreadShutdownContext>& context =
+    *currentThread->mRequestedShutdownContexts.AppendElement();
+  context = new nsThreadShutdownContext(WrapNotNull(this), currentThread, aSync);
+
+  // Set mShutdownContext and wake up the thread in case it is waiting for
+  // events to process.
+  nsCOMPtr<nsIRunnable> event =
+    new nsThreadShutdownEvent(WrapNotNull(this), WrapNotNull(context.get()));
+  // XXXroc What if posting the event fails due to OOM?
+  PutEvent(event.forget(), nullptr);
+
+  // We could still end up with other events being added after the shutdown
+  // task, but that's okay because we process pending events in ThreadFunc
+  // after setting mShutdownContext just before exiting.
+  return context;
+}
+
+void
+nsThread::ShutdownComplete(NotNull<nsThreadShutdownContext*> aContext)
+{
+  MOZ_ASSERT(mThread);
+  MOZ_ASSERT(aContext->mTerminatingThread == this);
+
+  if (aContext->mAwaitingShutdownAck) {
+    // We're in a synchronous shutdown, so tell whatever is up the stack that
+    // we're done and unwind the stack so it can call us again.
+    aContext->mAwaitingShutdownAck = false;
+    return;
+  }
+
+  // Now, it should be safe to join without fear of dead-locking.
+
+  PR_JoinThread(mThread);
+  mThread = nullptr;
+
+  // We hold strong references to our event observers, and once the thread is
+  // shut down the observers can't easily unregister themselves. Do it here
+  // to avoid leaking.
+  ClearObservers();
+
+#ifdef DEBUG
+  {
+    MutexAutoLock lock(mLock);
+    MOZ_ASSERT(!mObserver, "Should have been cleared at shutdown!");
+  }
+#endif
+
+  // Delete aContext.
+  MOZ_ALWAYS_TRUE(
+    aContext->mJoiningThread->mRequestedShutdownContexts.RemoveElement(aContext));
+}
+
+void
+nsThread::WaitForAllAsynchronousShutdowns()
+{
+  while (mRequestedShutdownContexts.Length()) {
+    NS_ProcessNextEvent(this, true);
+  }
+}
+
+NS_IMETHODIMP
+nsThread::Shutdown()
+{
+  LOG(("THRD(%p) sync shutdown\n", this));
+
+  // XXX If we make this warn, then we hit that warning at xpcom shutdown while
+  //     shutting down a thread in a thread pool.  That happens b/c the thread
+  //     in the thread pool is already shutdown by the thread manager.
+  if (!mThread) {
+    return NS_OK;
+  }
+
+  nsThreadShutdownContext* maybeContext = ShutdownInternal(/* aSync = */ true);
+  NS_ENSURE_TRUE(maybeContext, NS_ERROR_UNEXPECTED);
+  NotNull<nsThreadShutdownContext*> context = WrapNotNull(maybeContext);
+
+  // Process events on the current thread until we receive a shutdown ACK.
+  // Allows waiting; ensure no locks are held that would deadlock us!
+  while (context->mAwaitingShutdownAck) {
+    NS_ProcessNextEvent(context->mJoiningThread, true);
+  }
+
+  ShutdownComplete(context);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::HasPendingEvents(bool* aResult)
+{
+  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
+    return NS_ERROR_NOT_SAME_THREAD;
+  }
+
+  {
+    MutexAutoLock lock(mLock);
+    *aResult = mEvents->HasPendingEvent(lock);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::RegisterIdlePeriod(already_AddRefed<nsIIdlePeriod> aIdlePeriod)
+{
+  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
+    return NS_ERROR_NOT_SAME_THREAD;
+  }
+
+  MutexAutoLock lock(mLock);
+  mIdlePeriod = aIdlePeriod;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::IdleDispatch(already_AddRefed<nsIRunnable> aEvent)
+{
+  // Currently the only supported idle dispatch is from the same
+  // thread. To support idle dispatch from another thread we need to
+  // support waking threads that are waiting for an event queue that
+  // isn't mIdleEvents.
+  MOZ_ASSERT(PR_GetCurrentThread() == mThread);
+
+  MutexAutoLock lock(mLock);
+  LeakRefPtr<nsIRunnable> event(Move(aEvent));
+
+  if (NS_WARN_IF(!event)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  if (mEventsAreDoomed) {
+    NS_WARNING("An idle event was posted to a thread that will never run it (rejected)");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  mIdleEvents.PutEvent(event.take(), lock);
+  return NS_OK;
+}
+
+#ifdef MOZ_CANARY
+void canary_alarm_handler(int signum);
+
+class Canary
+{
+  //XXX ToDo: support nested loops
+public:
+  Canary()
+  {
+    if (sCanaryOutputFD > 0 && EventLatencyIsImportant()) {
+      signal(SIGALRM, canary_alarm_handler);
+      ualarm(15000, 0);
+    }
+  }
+
+  ~Canary()
+  {
+    if (sCanaryOutputFD != 0 && EventLatencyIsImportant()) {
+      ualarm(0, 0);
+    }
+  }
+
+  static bool EventLatencyIsImportant()
+  {
+    return NS_IsMainThread() && XRE_IsParentProcess();
+  }
+};
+
+void canary_alarm_handler(int signum)
+{
+  void* array[30];
+  const char msg[29] = "event took too long to run:\n";
+  // use write to be safe in the signal handler
+  write(sCanaryOutputFD, msg, sizeof(msg));
+  backtrace_symbols_fd(array, backtrace(array, 30), sCanaryOutputFD);
+}
+
+#endif
+
+#define NOTIFY_EVENT_OBSERVERS(func_, params_)                                 \
+  PR_BEGIN_MACRO                                                               \
+    if (!mEventObservers.IsEmpty()) {                                          \
+      nsAutoTObserverArray<NotNull<nsCOMPtr<nsIThreadObserver>>, 2>::ForwardIterator \
+        iter_(mEventObservers);                                                \
+      nsCOMPtr<nsIThreadObserver> obs_;                                        \
+      while (iter_.HasMore()) {                                                \
+        obs_ = iter_.GetNext();                                                \
+        obs_ -> func_ params_ ;                                                \
+      }                                                                        \
+    }                                                                          \
+  PR_END_MACRO
+
+void
+nsThread::GetIdleEvent(nsIRunnable** aEvent, MutexAutoLock& aProofOfLock)
+{
+  MOZ_ASSERT(PR_GetCurrentThread() == mThread);
+  MOZ_ASSERT(aEvent);
+
+  TimeStamp idleDeadline;
+  {
+    MutexAutoUnlock unlock(mLock);
+    mIdlePeriod->GetIdlePeriodHint(&idleDeadline);
+  }
+
+  if (!idleDeadline || idleDeadline < TimeStamp::Now()) {
+    aEvent = nullptr;
+    return;
+  }
+
+  mIdleEvents.GetEvent(false, aEvent, aProofOfLock);
+
+  if (*aEvent) {
+    nsCOMPtr<nsIIncrementalRunnable> incrementalEvent(do_QueryInterface(*aEvent));
+    if (incrementalEvent) {
+      incrementalEvent->SetDeadline(idleDeadline);
+    }
+  }
+}
+
+void
+nsThread::GetEvent(bool aWait, nsIRunnable** aEvent, MutexAutoLock& aProofOfLock)
+{
+  MOZ_ASSERT(PR_GetCurrentThread() == mThread);
+  MOZ_ASSERT(aEvent);
+
+  // We'll try to get an event to execute in three stages.
+  // [1] First we just try to get it from the regular queue without waiting.
+  mEvents->GetEvent(false, aEvent, aProofOfLock);
+
+  // [2] If we didn't get an event from the regular queue, try to
+  // get one from the idle queue
+  if (!*aEvent) {
+    // Since events in mEvents have higher priority than idle
+    // events, we will only consider idle events when there are no
+    // pending events in mEvents. We will for the same reason never
+    // wait for an idle event, since a higher priority event might
+    // appear at any time.
+    GetIdleEvent(aEvent, aProofOfLock);
+  }
+
+  // [3] If we neither got an event from the regular queue nor the
+  // idle queue, then if we should wait for events we block on the
+  // main queue until an event is available.
+  // If we are shutting down, then do not wait for new events.
+  if (!*aEvent && aWait) {
+    mEvents->GetEvent(aWait, aEvent, aProofOfLock);
+  }
+}
+
+NS_IMETHODIMP
+nsThread::ProcessNextEvent(bool aMayWait, bool* aResult)
+{
+  LOG(("THRD(%p) ProcessNextEvent [%u %u]\n", this, aMayWait,
+       mNestedEventLoopDepth));
+
+  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
+    return NS_ERROR_NOT_SAME_THREAD;
+  }
+
+  // The toplevel event loop normally blocks waiting for the next event, but
+  // if we're trying to shut this thread down, we must exit the event loop when
+  // the event queue is empty.
+  // This only applys to the toplevel event loop! Nested event loops (e.g.
+  // during sync dispatch) are waiting for some state change and must be able
+  // to block even if something has requested shutdown of the thread. Otherwise
+  // we'll just busywait as we endlessly look for an event, fail to find one,
+  // and repeat the nested event loop since its state change hasn't happened yet.
+  bool reallyWait = aMayWait && (mNestedEventLoopDepth > 0 || !ShuttingDown());
+
+  if (mIsMainThread == MAIN_THREAD) {
+    DoMainThreadSpecificProcessing(reallyWait);
+  }
+
+  ++mNestedEventLoopDepth;
+
+  // We only want to create an AutoNoJSAPI on threads that actually do DOM stuff
+  // (including workers).  Those are exactly the threads that have an
+  // mScriptObserver.
+  Maybe<dom::AutoNoJSAPI> noJSAPI;
+  bool callScriptObserver = !!mScriptObserver;
+  if (callScriptObserver) {
+    noJSAPI.emplace();
+    mScriptObserver->BeforeProcessTask(reallyWait);
+  }
+
+  nsCOMPtr<nsIThreadObserver> obs = mObserver;
+  if (obs) {
+    obs->OnProcessNextEvent(this, reallyWait);
+  }
+
+  NOTIFY_EVENT_OBSERVERS(OnProcessNextEvent, (this, reallyWait));
+
+#ifdef MOZ_CANARY
+  Canary canary;
+#endif
+  nsresult rv = NS_OK;
+
+  {
+    // Scope for |event| to make sure that its destructor fires while
+    // mNestedEventLoopDepth has been incremented, since that destructor can
+    // also do work.
+    nsCOMPtr<nsIRunnable> event;
+    {
+      MutexAutoLock lock(mLock);
+      GetEvent(reallyWait, getter_AddRefs(event), lock);
+    }
+
+    *aResult = (event.get() != nullptr);
+
+    if (event) {
+      LOG(("THRD(%p) running [%p]\n", this, event.get()));
+      if (MAIN_THREAD == mIsMainThread) {
+        HangMonitor::NotifyActivity();
+      }
+      event->Run();
+    } else if (aMayWait) {
+      MOZ_ASSERT(ShuttingDown(),
+                 "This should only happen when shutting down");
+      rv = NS_ERROR_UNEXPECTED;
+    }
+  }
+
+  NOTIFY_EVENT_OBSERVERS(AfterProcessNextEvent, (this, *aResult));
+
+  if (obs) {
+    obs->AfterProcessNextEvent(this, *aResult);
+  }
+
+  if (callScriptObserver) {
+    if (mScriptObserver) {
+      mScriptObserver->AfterProcessTask(mNestedEventLoopDepth);
+    }
+    noJSAPI.reset();
+  }
+
+  --mNestedEventLoopDepth;
+
+  return rv;
+}
+
+//-----------------------------------------------------------------------------
+// nsISupportsPriority
+
+NS_IMETHODIMP
+nsThread::GetPriority(int32_t* aPriority)
+{
+  *aPriority = mPriority;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::SetPriority(int32_t aPriority)
+{
+  if (NS_WARN_IF(!mThread)) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  // NSPR defines the following four thread priorities:
+  //   PR_PRIORITY_LOW
+  //   PR_PRIORITY_NORMAL
+  //   PR_PRIORITY_HIGH
+  //   PR_PRIORITY_URGENT
+  // We map the priority values defined on nsISupportsPriority to these values.
+
+  mPriority = aPriority;
+
+  PRThreadPriority pri;
+  if (mPriority <= PRIORITY_HIGHEST) {
+    pri = PR_PRIORITY_URGENT;
+  } else if (mPriority < PRIORITY_NORMAL) {
+    pri = PR_PRIORITY_HIGH;
+  } else if (mPriority > PRIORITY_NORMAL) {
+    pri = PR_PRIORITY_LOW;
+  } else {
+    pri = PR_PRIORITY_NORMAL;
+  }
+  // If chaos mode is active, retain the randomly chosen priority
+  if (!ChaosMode::isActive(ChaosFeature::ThreadScheduling)) {
+    PR_SetThreadPriority(mThread, pri);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::AdjustPriority(int32_t aDelta)
+{
+  return SetPriority(mPriority + aDelta);
+}
+
+//-----------------------------------------------------------------------------
+// nsIThreadInternal
+
+NS_IMETHODIMP
+nsThread::GetObserver(nsIThreadObserver** aObs)
+{
+  MutexAutoLock lock(mLock);
+  NS_IF_ADDREF(*aObs = mObserver);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::SetObserver(nsIThreadObserver* aObs)
+{
+  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
+    return NS_ERROR_NOT_SAME_THREAD;
+  }
+
+  MutexAutoLock lock(mLock);
+  mObserver = aObs;
+  return NS_OK;
+}
+
+uint32_t
+nsThread::RecursionDepth() const
+{
+  MOZ_ASSERT(PR_GetCurrentThread() == mThread);
+  return mNestedEventLoopDepth;
+}
+
+NS_IMETHODIMP
+nsThread::AddObserver(nsIThreadObserver* aObserver)
+{
+  if (NS_WARN_IF(!aObserver)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
+    return NS_ERROR_NOT_SAME_THREAD;
+  }
+
+  NS_WARNING_ASSERTION(!mEventObservers.Contains(aObserver),
+                       "Adding an observer twice!");
+
+  if (!mEventObservers.AppendElement(WrapNotNull(aObserver))) {
+    NS_WARNING("Out of memory!");
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::RemoveObserver(nsIThreadObserver* aObserver)
+{
+  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
+    return NS_ERROR_NOT_SAME_THREAD;
+  }
+
+  if (aObserver && !mEventObservers.RemoveElement(aObserver)) {
+    NS_WARNING("Removing an observer that was never added!");
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::PushEventQueue(nsIEventTarget** aResult)
+{
+  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
+    return NS_ERROR_NOT_SAME_THREAD;
+  }
+
+  NotNull<nsChainedEventQueue*> queue =
+    WrapNotNull(new nsChainedEventQueue(mLock));
+  queue->mEventTarget = new nsNestedEventTarget(WrapNotNull(this), queue);
+
+  {
+    MutexAutoLock lock(mLock);
+    queue->mNext = mEvents;
+    mEvents = queue;
+  }
+
+  NS_ADDREF(*aResult = queue->mEventTarget);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThread::PopEventQueue(nsIEventTarget* aInnermostTarget)
+{
+  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
+    return NS_ERROR_NOT_SAME_THREAD;
+  }
+
+  if (NS_WARN_IF(!aInnermostTarget)) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  // Don't delete or release anything while holding the lock.
+  nsAutoPtr<nsChainedEventQueue> queue;
+  RefPtr<nsNestedEventTarget> target;
+
+  {
+    MutexAutoLock lock(mLock);
+
+    // Make sure we're popping the innermost event target.
+    if (NS_WARN_IF(mEvents->mEventTarget != aInnermostTarget)) {
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    MOZ_ASSERT(mEvents != &mEventsRoot);
+
+    queue = mEvents;
+    mEvents = WrapNotNull(mEvents->mNext);
+
+    nsCOMPtr<nsIRunnable> event;
+    while (queue->GetEvent(false, getter_AddRefs(event), lock)) {
+      mEvents->PutEvent(event.forget(), lock);
+    }
+
+    // Don't let the event target post any more events.
+    queue->mEventTarget.swap(target);
+    target->mQueue = nullptr;
+  }
+
+  return NS_OK;
+}
+
+void
+nsThread::SetScriptObserver(mozilla::CycleCollectedJSContext* aScriptObserver)
+{
+  if (!aScriptObserver) {
+    mScriptObserver = nullptr;
+    return;
+  }
+
+  MOZ_ASSERT(!mScriptObserver);
+  mScriptObserver = aScriptObserver;
+}
+
+void
+nsThread::DoMainThreadSpecificProcessing(bool aReallyWait)
+{
+  MOZ_ASSERT(mIsMainThread == MAIN_THREAD);
+
+  ipc::CancelCPOWs();
+
+  if (aReallyWait) {
+    HangMonitor::Suspend();
+  }
+
+  // Fire a memory pressure notification, if one is pending.
+  if (!ShuttingDown()) {
+    MemoryPressureState mpPending = NS_GetPendingMemoryPressure();
+    if (mpPending != MemPressure_None) {
+      nsCOMPtr<nsIObserverService> os = services::GetObserverService();
+
+      // Use no-forward to prevent the notifications from being transferred to
+      // the children of this process.
+      NS_NAMED_LITERAL_STRING(lowMem, "low-memory-no-forward");
+      NS_NAMED_LITERAL_STRING(lowMemOngoing, "low-memory-ongoing-no-forward");
+
+      if (os) {
+        os->NotifyObservers(nullptr, "memory-pressure",
+                            mpPending == MemPressure_New ? lowMem.get() :
+                            lowMemOngoing.get());
+      } else {
+        NS_WARNING("Can't get observer service!");
+      }
+    }
+  }
+
+#ifdef MOZ_CRASHREPORTER
+  if (!ShuttingDown()) {
+    SaveMemoryReportNearOOM(ShouldSaveMemoryReport::kMaybeReport);
+  }
+#endif
+}
+
+//-----------------------------------------------------------------------------
+
+NS_IMPL_ISUPPORTS(nsThread::nsNestedEventTarget, nsIEventTarget)
+
+NS_IMETHODIMP
+nsThread::nsNestedEventTarget::DispatchFromScript(nsIRunnable* aEvent, uint32_t aFlags)
+{
+  nsCOMPtr<nsIRunnable> event(aEvent);
+  return Dispatch(event.forget(), aFlags);
+}
+
+NS_IMETHODIMP
+nsThread::nsNestedEventTarget::Dispatch(already_AddRefed<nsIRunnable> aEvent, uint32_t aFlags)
+{
+  LOG(("THRD(%p) Dispatch [%p %x] to nested loop %p\n", mThread.get().get(),
+       /*XXX aEvent*/ nullptr, aFlags, this));
+
+  return mThread->DispatchInternal(Move(aEvent), aFlags, this);
+}
+
+NS_IMETHODIMP
+nsThread::nsNestedEventTarget::DelayedDispatch(already_AddRefed<nsIRunnable>, uint32_t)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsThread::nsNestedEventTarget::IsOnCurrentThread(bool* aResult)
+{
+  return mThread->IsOnCurrentThread(aResult);
+}