xpcom/threads/LazyIdleThread.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "LazyIdleThread.h"
   8
   9 #include "nsIObserverService.h"
  10
  11 #include "GeckoProfiler.h"
  12 #include "nsComponentManagerUtils.h"
  13 #include "nsServiceManagerUtils.h"
  14 #include "nsThreadUtils.h"
  15 #include "mozilla/Services.h"
  16
  17 #ifdef DEBUG
  18 #  define ASSERT_OWNING_THREAD()                           \
  19     do {                                                   \
  20       MOZ_ASSERT(mOwningEventTarget->IsOnCurrentThread()); \
  21     } while (0)
  22 #else
  23 #  define ASSERT_OWNING_THREAD() /* nothing */
  24 #endif
  25
  26 namespace mozilla {
  27
  28 LazyIdleThread::LazyIdleThread(uint32_t aIdleTimeoutMS, const nsACString& aName,
  29                                ShutdownMethod aShutdownMethod,
  30                                nsIObserver* aIdleObserver)
  31     : mMutex("LazyIdleThread::mMutex"),
  32       mOwningEventTarget(GetCurrentSerialEventTarget()),
  33       mIdleObserver(aIdleObserver),
  34       mQueuedRunnables(nullptr),
  35       mIdleTimeoutMS(aIdleTimeoutMS),
  36       mPendingEventCount(0),
  37       mIdleNotificationCount(0),
  38       mShutdownMethod(aShutdownMethod),
  39       mShutdown(false),
  40       mThreadIsShuttingDown(false),
  41       mIdleTimeoutEnabled(true),
  42       mName(aName) {
  43   MOZ_ASSERT(mOwningEventTarget, "Need owning thread!");
  44 }
  45
  46 LazyIdleThread::~LazyIdleThread() {
  47   ASSERT_OWNING_THREAD();
  48
  49   Shutdown();
  50 }
  51
  52 void LazyIdleThread::SetWeakIdleObserver(nsIObserver* aObserver) {
  53   ASSERT_OWNING_THREAD();
  54
  55   if (mShutdown) {
  56     NS_WARNING_ASSERTION(!aObserver,
  57                          "Setting an observer after Shutdown was called!");
  58     return;
  59   }
  60
  61   mIdleObserver = aObserver;
  62 }
  63
  64 void LazyIdleThread::DisableIdleTimeout() {
  65   ASSERT_OWNING_THREAD();
  66   if (!mIdleTimeoutEnabled) {
  67     return;
  68   }
  69   mIdleTimeoutEnabled = false;
  70
  71   if (mIdleTimer && NS_FAILED(mIdleTimer->Cancel())) {
  72     NS_WARNING("Failed to cancel timer!");
  73   }
  74
  75   MutexAutoLock lock(mMutex);
  76
  77   // Pretend we have a pending event to keep the idle timer from firing.
  78   MOZ_ASSERT(mPendingEventCount < UINT32_MAX, "Way too many!");
  79   mPendingEventCount++;
  80 }
  81
  82 void LazyIdleThread::EnableIdleTimeout() {
  83   ASSERT_OWNING_THREAD();
  84   if (mIdleTimeoutEnabled) {
  85     return;
  86   }
  87   mIdleTimeoutEnabled = true;
  88
  89   {
  90     MutexAutoLock lock(mMutex);
  91
  92     MOZ_ASSERT(mPendingEventCount, "Mismatched calls to observer methods!");
  93     --mPendingEventCount;
  94   }
  95
  96   if (mThread) {
  97     nsCOMPtr<nsIRunnable> runnable(new Runnable("LazyIdleThreadDummyRunnable"));
  98     if (NS_FAILED(Dispatch(runnable.forget(), NS_DISPATCH_NORMAL))) {
  99       NS_WARNING("Failed to dispatch!");
 100     }
 101   }
 102 }
 103
 104 void LazyIdleThread::PreDispatch() {
 105   MutexAutoLock lock(mMutex);
 106
 107   MOZ_ASSERT(mPendingEventCount < UINT32_MAX, "Way too many!");
 108   mPendingEventCount++;
 109 }
 110
 111 nsresult LazyIdleThread::EnsureThread() {
 112   ASSERT_OWNING_THREAD();
 113
 114   if (mShutdown) {
 115     return NS_ERROR_UNEXPECTED;
 116   }
 117
 118   if (mThread) {
 119     return NS_OK;
 120   }
 121
 122   MOZ_ASSERT(!mPendingEventCount, "Shouldn't have events yet!");
 123   MOZ_ASSERT(!mIdleNotificationCount, "Shouldn't have idle events yet!");
 124   MOZ_ASSERT(!mIdleTimer, "Should have killed this long ago!");
 125   MOZ_ASSERT(!mThreadIsShuttingDown, "Should have cleared that!");
 126
 127   nsresult rv;
 128
 129   if (mShutdownMethod == AutomaticShutdown && NS_IsMainThread()) {
 130     nsCOMPtr<nsIObserverService> obs =
 131         do_GetService(NS_OBSERVERSERVICE_CONTRACTID, &rv);
 132     if (NS_WARN_IF(NS_FAILED(rv))) {
 133       return rv;
 134     }
 135
 136     rv = obs->AddObserver(this, "xpcom-shutdown-threads", false);
 137     if (NS_WARN_IF(NS_FAILED(rv))) {
 138       return rv;
 139     }
 140   }
 141
 142   mIdleTimer = NS_NewTimer();
 143   if (NS_WARN_IF(!mIdleTimer)) {
 144     return NS_ERROR_UNEXPECTED;
 145   }
 146
 147   nsCOMPtr<nsIRunnable> runnable = NewRunnableMethod(
 148       "LazyIdleThread::InitThread", this, &LazyIdleThread::InitThread);
 149   if (NS_WARN_IF(!runnable)) {
 150     return NS_ERROR_UNEXPECTED;
 151   }
 152
 153   rv = NS_NewNamedThread(mName, getter_AddRefs(mThread), runnable);
 154   if (NS_WARN_IF(NS_FAILED(rv))) {
 155     return rv;
 156   }
 157
 158   return NS_OK;
 159 }
 160
 161 void LazyIdleThread::InitThread() {
 162   // Happens on mThread but mThread may not be set yet...
 163
 164   nsCOMPtr<nsIThreadInternal> thread(do_QueryInterface(NS_GetCurrentThread()));
 165   MOZ_ASSERT(thread, "This should always succeed!");
 166
 167   if (NS_FAILED(thread->SetObserver(this))) {
 168     NS_WARNING("Failed to set thread observer!");
 169   }
 170 }
 171
 172 void LazyIdleThread::CleanupThread() {
 173   nsCOMPtr<nsIThreadInternal> thread(do_QueryInterface(NS_GetCurrentThread()));
 174   MOZ_ASSERT(thread, "This should always succeed!");
 175
 176   if (NS_FAILED(thread->SetObserver(nullptr))) {
 177     NS_WARNING("Failed to set thread observer!");
 178   }
 179
 180   {
 181     MutexAutoLock lock(mMutex);
 182
 183     MOZ_ASSERT(!mThreadIsShuttingDown, "Shouldn't be true ever!");
 184     mThreadIsShuttingDown = true;
 185   }
 186 }
 187
 188 void LazyIdleThread::ScheduleTimer() {
 189   ASSERT_OWNING_THREAD();
 190
 191   bool shouldSchedule;
 192   {
 193     MutexAutoLock lock(mMutex);
 194
 195     MOZ_ASSERT(mIdleNotificationCount, "Should have at least one!");
 196     --mIdleNotificationCount;
 197
 198     shouldSchedule = !mIdleNotificationCount && !mPendingEventCount;
 199   }
 200
 201   if (mIdleTimer) {
 202     if (NS_FAILED(mIdleTimer->Cancel())) {
 203       NS_WARNING("Failed to cancel timer!");
 204     }
 205
 206     if (shouldSchedule && NS_FAILED(mIdleTimer->InitWithCallback(
 207                               this, mIdleTimeoutMS, nsITimer::TYPE_ONE_SHOT))) {
 208       NS_WARNING("Failed to schedule timer!");
 209     }
 210   }
 211 }
 212
 213 nsresult LazyIdleThread::ShutdownThread() {
 214   ASSERT_OWNING_THREAD();
 215
 216   // Before calling Shutdown() on the real thread we need to put a queue in
 217   // place in case a runnable is posted to the thread while it's in the
 218   // process of shutting down. This will be our queue.
 219   AutoTArray<nsCOMPtr<nsIRunnable>, 10> queuedRunnables;
 220
 221   nsresult rv;
 222
 223   // Make sure to cancel the shutdown timer before spinning the event loop
 224   // during |mThread->Shutdown()| below. Otherwise the timer might fire and we
 225   // could reenter here.
 226   if (mIdleTimer) {
 227     rv = mIdleTimer->Cancel();
 228     if (NS_WARN_IF(NS_FAILED(rv))) {
 229       return rv;
 230     }
 231
 232     mIdleTimer = nullptr;
 233   }
 234
 235   if (mThread) {
 236     if (mShutdownMethod == AutomaticShutdown && NS_IsMainThread()) {
 237       nsCOMPtr<nsIObserverService> obs =
 238           mozilla::services::GetObserverService();
 239       NS_WARNING_ASSERTION(obs, "Failed to get observer service!");
 240
 241       if (obs &&
 242           NS_FAILED(obs->RemoveObserver(this, "xpcom-shutdown-threads"))) {
 243         NS_WARNING("Failed to remove observer!");
 244       }
 245     }
 246
 247     if (mIdleObserver) {
 248       mIdleObserver->Observe(static_cast<nsIThread*>(this), IDLE_THREAD_TOPIC,
 249                              nullptr);
 250     }
 251
 252 #ifdef DEBUG
 253     {
 254       MutexAutoLock lock(mMutex);
 255       MOZ_ASSERT(!mThreadIsShuttingDown, "Huh?!");
 256     }
 257 #endif
 258
 259     nsCOMPtr<nsIRunnable> runnable = NewRunnableMethod(
 260         "LazyIdleThread::CleanupThread", this, &LazyIdleThread::CleanupThread);
 261     if (NS_WARN_IF(!runnable)) {
 262       return NS_ERROR_UNEXPECTED;
 263     }
 264
 265     PreDispatch();
 266
 267     rv = mThread->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
 268     if (NS_WARN_IF(NS_FAILED(rv))) {
 269       return rv;
 270     }
 271
 272     // Put the temporary queue in place before calling Shutdown().
 273     mQueuedRunnables = &queuedRunnables;
 274
 275     if (NS_FAILED(mThread->Shutdown())) {
 276       NS_ERROR("Failed to shutdown the thread!");
 277     }
 278
 279     // Now unset the queue.
 280     mQueuedRunnables = nullptr;
 281
 282     mThread = nullptr;
 283
 284     {
 285       MutexAutoLock lock(mMutex);
 286
 287       MOZ_ASSERT(!mPendingEventCount, "Huh?!");
 288       MOZ_ASSERT(!mIdleNotificationCount, "Huh?!");
 289       MOZ_ASSERT(mThreadIsShuttingDown, "Huh?!");
 290       mThreadIsShuttingDown = false;
 291     }
 292   }
 293
 294   // If our temporary queue has any runnables then we need to dispatch them.
 295   if (queuedRunnables.Length()) {
 296     // If the thread manager has gone away then these runnables will never run.
 297     if (mShutdown) {
 298       NS_ERROR("Runnables dispatched to LazyIdleThread will never run!");
 299       return NS_OK;
 300     }
 301
 302     // Re-dispatch the queued runnables.
 303     for (uint32_t index = 0; index < queuedRunnables.Length(); index++) {
 304       nsCOMPtr<nsIRunnable> runnable;
 305       runnable.swap(queuedRunnables[index]);
 306       MOZ_ASSERT(runnable, "Null runnable?!");
 307
 308       if (NS_FAILED(Dispatch(runnable.forget(), NS_DISPATCH_NORMAL))) {
 309         NS_ERROR("Failed to re-dispatch queued runnable!");
 310       }
 311     }
 312   }
 313
 314   return NS_OK;
 315 }
 316
 317 void LazyIdleThread::SelfDestruct() {
 318   MOZ_ASSERT(mRefCnt == 1, "Bad refcount!");
 319   delete this;
 320 }
 321
 322 NS_IMPL_ADDREF(LazyIdleThread)
 323
 324 NS_IMETHODIMP_(MozExternalRefCountType)
 325 LazyIdleThread::Release() {
 326   nsrefcnt count = --mRefCnt;
 327   NS_LOG_RELEASE(this, count, "LazyIdleThread");
 328
 329   if (!count) {
 330     // Stabilize refcount.
 331     mRefCnt = 1;
 332
 333     nsCOMPtr<nsIRunnable> runnable = NewNonOwningRunnableMethod(
 334         "LazyIdleThread::SelfDestruct", this, &LazyIdleThread::SelfDestruct);
 335     NS_WARNING_ASSERTION(runnable, "Couldn't make runnable!");
 336
 337     if (NS_FAILED(NS_DispatchToCurrentThread(runnable))) {
 338       MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
 339       // The only way this could fail is if we're in shutdown, and in that case
 340       // threads should have been joined already. Deleting here isn't dangerous
 341       // anymore because we won't spin the event loop waiting to join the
 342       // thread.
 343       SelfDestruct();
 344     }
 345   }
 346
 347   return count;
 348 }
 349
 350 NS_IMPL_QUERY_INTERFACE(LazyIdleThread, nsIThread, nsIEventTarget,
 351                         nsISerialEventTarget, nsITimerCallback,
 352                         nsIThreadObserver, nsIObserver, nsINamed)
 353
 354 NS_IMETHODIMP
 355 LazyIdleThread::DispatchFromScript(nsIRunnable* aEvent, uint32_t aFlags) {
 356   nsCOMPtr<nsIRunnable> event(aEvent);
 357   return Dispatch(event.forget(), aFlags);
 358 }
 359
 360 NS_IMETHODIMP
 361 LazyIdleThread::Dispatch(already_AddRefed<nsIRunnable> aEvent,
 362                          uint32_t aFlags) {
 363   ASSERT_OWNING_THREAD();
 364   nsCOMPtr<nsIRunnable> event(aEvent);  // avoid leaks
 365
 366   // LazyIdleThread can't always support synchronous dispatch currently.
 367   if (NS_WARN_IF(aFlags != NS_DISPATCH_NORMAL)) {
 368     return NS_ERROR_NOT_IMPLEMENTED;
 369   }
 370
 371   if (NS_WARN_IF(mShutdown)) {
 372     return NS_ERROR_UNEXPECTED;
 373   }
 374
 375   // If our thread is shutting down then we can't actually dispatch right now.
 376   // Queue this runnable for later.
 377   if (UseRunnableQueue()) {
 378     mQueuedRunnables->AppendElement(event);
 379     return NS_OK;
 380   }
 381
 382   nsresult rv = EnsureThread();
 383   if (NS_WARN_IF(NS_FAILED(rv))) {
 384     return rv;
 385   }
 386
 387   PreDispatch();
 388
 389   return mThread->Dispatch(event.forget(), aFlags);
 390 }
 391
 392 NS_IMETHODIMP
 393 LazyIdleThread::DelayedDispatch(already_AddRefed<nsIRunnable>, uint32_t) {
 394   return NS_ERROR_NOT_IMPLEMENTED;
 395 }
 396
 397 NS_IMETHODIMP
 398 LazyIdleThread::GetRunningEventDelay(TimeDuration* aDelay, TimeStamp* aStart) {
 399   if (mThread) {
 400     return mThread->GetRunningEventDelay(aDelay, aStart);
 401   }
 402   *aDelay = TimeDuration();
 403   *aStart = TimeStamp();
 404   return NS_OK;
 405 }
 406
 407 NS_IMETHODIMP
 408 LazyIdleThread::SetRunningEventDelay(TimeDuration aDelay, TimeStamp aStart) {
 409   if (mThread) {
 410     return mThread->SetRunningEventDelay(aDelay, aStart);
 411   }
 412   return NS_OK;
 413 }
 414
 415 NS_IMETHODIMP
 416 LazyIdleThread::IsOnCurrentThread(bool* aIsOnCurrentThread) {
 417   if (mThread) {
 418     return mThread->IsOnCurrentThread(aIsOnCurrentThread);
 419   }
 420
 421   *aIsOnCurrentThread = false;
 422   return NS_OK;
 423 }
 424
 425 NS_IMETHODIMP_(bool)
 426 LazyIdleThread::IsOnCurrentThreadInfallible() {
 427   if (mThread) {
 428     return mThread->IsOnCurrentThread();
 429   }
 430
 431   return false;
 432 }
 433
 434 NS_IMETHODIMP
 435 LazyIdleThread::GetPRThread(PRThread** aPRThread) {
 436   if (mThread) {
 437     return mThread->GetPRThread(aPRThread);
 438   }
 439
 440   *aPRThread = nullptr;
 441   return NS_ERROR_NOT_AVAILABLE;
 442 }
 443
 444 NS_IMETHODIMP
 445 LazyIdleThread::GetCanInvokeJS(bool* aCanInvokeJS) {
 446   *aCanInvokeJS = false;
 447   return NS_OK;
 448 }
 449
 450 NS_IMETHODIMP
 451 LazyIdleThread::SetCanInvokeJS(bool aCanInvokeJS) {
 452   return NS_ERROR_NOT_IMPLEMENTED;
 453 }
 454
 455 NS_IMETHODIMP
 456 LazyIdleThread::GetLastLongTaskEnd(TimeStamp* _retval) {
 457   return NS_ERROR_NOT_IMPLEMENTED;
 458 }
 459
 460 NS_IMETHODIMP
 461 LazyIdleThread::GetLastLongNonIdleTaskEnd(TimeStamp* _retval) {
 462   return NS_ERROR_NOT_IMPLEMENTED;
 463 }
 464
 465 NS_IMETHODIMP
 466 LazyIdleThread::SetNameForWakeupTelemetry(const nsACString& aName) {
 467   return NS_ERROR_NOT_IMPLEMENTED;
 468 }
 469
 470 NS_IMETHODIMP
 471 LazyIdleThread::AsyncShutdown() {
 472   ASSERT_OWNING_THREAD();
 473   return NS_ERROR_NOT_IMPLEMENTED;
 474 }
 475
 476 NS_IMETHODIMP
 477 LazyIdleThread::BeginShutdown(nsIThreadShutdown** aShutdown) {
 478   ASSERT_OWNING_THREAD();
 479   *aShutdown = nullptr;
 480   return NS_ERROR_NOT_IMPLEMENTED;
 481 }
 482
 483 NS_IMETHODIMP
 484 LazyIdleThread::Shutdown() {
 485   ASSERT_OWNING_THREAD();
 486
 487   mShutdown = true;
 488
 489   nsresult rv = ShutdownThread();
 490   MOZ_ASSERT(!mThread, "Should have destroyed this by now!");
 491
 492   mIdleObserver = nullptr;
 493
 494   if (NS_WARN_IF(NS_FAILED(rv))) {
 495     return rv;
 496   }
 497
 498   return NS_OK;
 499 }
 500
 501 NS_IMETHODIMP
 502 LazyIdleThread::HasPendingEvents(bool* aHasPendingEvents) {
 503   // This is only supposed to be called from the thread itself so it's not
 504   // implemented here.
 505   MOZ_ASSERT_UNREACHABLE("Shouldn't ever call this!");
 506   return NS_ERROR_UNEXPECTED;
 507 }
 508
 509 NS_IMETHODIMP
 510 LazyIdleThread::HasPendingHighPriorityEvents(bool* aHasPendingEvents) {
 511   // This is only supposed to be called from the thread itself so it's not
 512   // implemented here.
 513   MOZ_ASSERT_UNREACHABLE("Shouldn't ever call this!");
 514   return NS_ERROR_UNEXPECTED;
 515 }
 516
 517 NS_IMETHODIMP
 518 LazyIdleThread::DispatchToQueue(already_AddRefed<nsIRunnable> aEvent,
 519                                 EventQueuePriority aQueue) {
 520   return NS_ERROR_NOT_IMPLEMENTED;
 521 }
 522
 523 NS_IMETHODIMP
 524 LazyIdleThread::ProcessNextEvent(bool aMayWait, bool* aEventWasProcessed) {
 525   // This is only supposed to be called from the thread itself so it's not
 526   // implemented here.
 527   MOZ_ASSERT_UNREACHABLE("Shouldn't ever call this!");
 528   return NS_ERROR_UNEXPECTED;
 529 }
 530
 531 NS_IMETHODIMP
 532 LazyIdleThread::Notify(nsITimer* aTimer) {
 533   ASSERT_OWNING_THREAD();
 534
 535   {
 536     MutexAutoLock lock(mMutex);
 537
 538     if (mPendingEventCount || mIdleNotificationCount) {
 539       // Another event was scheduled since this timer was set. Don't do
 540       // anything and wait for the timer to fire again.
 541       return NS_OK;
 542     }
 543   }
 544
 545   nsresult rv = ShutdownThread();
 546   if (NS_WARN_IF(NS_FAILED(rv))) {
 547     return rv;
 548   }
 549
 550   return NS_OK;
 551 }
 552
 553 NS_IMETHODIMP
 554 LazyIdleThread::GetName(nsACString& aName) {
 555   aName.Assign(mName);
 556   return NS_OK;
 557 }
 558
 559 NS_IMETHODIMP
 560 LazyIdleThread::OnDispatchedEvent() {
 561   MOZ_ASSERT(mOwningEventTarget->IsOnCurrentThread());
 562   return NS_OK;
 563 }
 564
 565 NS_IMETHODIMP
 566 LazyIdleThread::OnProcessNextEvent(nsIThreadInternal* /* aThread */,
 567                                    bool /* aMayWait */) {
 568   return NS_OK;
 569 }
 570
 571 NS_IMETHODIMP
 572 LazyIdleThread::AfterProcessNextEvent(nsIThreadInternal* /* aThread */,
 573                                       bool aEventWasProcessed) {
 574   bool shouldNotifyIdle;
 575   {
 576     MutexAutoLock lock(mMutex);
 577
 578     if (aEventWasProcessed) {
 579       MOZ_ASSERT(mPendingEventCount, "Mismatched calls to observer methods!");
 580       --mPendingEventCount;
 581     }
 582
 583     if (mThreadIsShuttingDown) {
 584       // We're shutting down, no need to fire any timer.
 585       return NS_OK;
 586     }
 587
 588     shouldNotifyIdle = !mPendingEventCount;
 589     if (shouldNotifyIdle) {
 590       MOZ_ASSERT(mIdleNotificationCount < UINT32_MAX, "Way too many!");
 591       mIdleNotificationCount++;
 592     }
 593   }
 594
 595   if (shouldNotifyIdle) {
 596     nsCOMPtr<nsIRunnable> runnable = NewRunnableMethod(
 597         "LazyIdleThread::ScheduleTimer", this, &LazyIdleThread::ScheduleTimer);
 598     if (NS_WARN_IF(!runnable)) {
 599       return NS_ERROR_UNEXPECTED;
 600     }
 601
 602     nsresult rv =
 603         mOwningEventTarget->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
 604     if (NS_WARN_IF(NS_FAILED(rv))) {
 605       return rv;
 606     }
 607   }
 608
 609   return NS_OK;
 610 }
 611
 612 NS_IMETHODIMP
 613 LazyIdleThread::Observe(nsISupports* /* aSubject */, const char* aTopic,
 614                         const char16_t* /* aData */) {
 615   MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
 616   MOZ_ASSERT(mShutdownMethod == AutomaticShutdown,
 617              "Should not receive notifications if not AutomaticShutdown!");
 618   MOZ_ASSERT(!strcmp("xpcom-shutdown-threads", aTopic), "Bad topic!");
 619
 620   Shutdown();
 621   return NS_OK;
 622 }
 623
 624 NS_IMETHODIMP
 625 LazyIdleThread::GetEventTarget(nsIEventTarget** aEventTarget) {
 626   nsCOMPtr<nsIEventTarget> target = this;
 627   target.forget(aEventTarget);
 628   return NS_OK;
 629 }
 630
 631 nsIEventTarget* LazyIdleThread::EventTarget() { return this; }
 632
 633 nsISerialEventTarget* LazyIdleThread::SerialEventTarget() { return this; }
 634
 635 }  // namespace mozilla