mirror of
https://github.com/classilla/tenfourfox.git
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230 lines
6.4 KiB
C++
230 lines
6.4 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_lazyidlethread_h__
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#define mozilla_lazyidlethread_h__
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#ifndef MOZILLA_INTERNAL_API
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#error "This header is only usable from within libxul (MOZILLA_INTERNAL_API)."
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#endif
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#include "nsIObserver.h"
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#include "nsIThreadInternal.h"
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#include "nsITimer.h"
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#include "mozilla/Mutex.h"
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#include "nsCOMPtr.h"
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#include "nsTArray.h"
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#include "nsString.h"
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#include "mozilla/Attributes.h"
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#define IDLE_THREAD_TOPIC "thread-shutting-down"
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namespace mozilla {
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/**
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* This class provides a basic event target that creates its thread lazily and
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* destroys its thread after a period of inactivity. It may be created on any
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* thread but it may only be used from the thread on which it is created. If it
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* is created on the main thread then it will automatically join its thread on
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* XPCOM shutdown using the Observer Service.
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*/
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class LazyIdleThread final
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: public nsIThread
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, public nsITimerCallback
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, public nsIThreadObserver
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, public nsIObserver
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{
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public:
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NS_DECL_THREADSAFE_ISUPPORTS
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NS_DECL_NSIEVENTTARGET
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NS_DECL_NSITHREAD
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NS_DECL_NSITIMERCALLBACK
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NS_DECL_NSITHREADOBSERVER
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NS_DECL_NSIOBSERVER
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// missing from NS_DECL_NSIEVENTTARGET because MSVC
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nsresult Dispatch(nsIRunnable* aEvent, uint32_t aFlags) {
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return Dispatch(nsCOMPtr<nsIRunnable>(aEvent).forget(), aFlags);
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}
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enum ShutdownMethod
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{
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AutomaticShutdown = 0,
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ManualShutdown
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};
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/**
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* Create a new LazyIdleThread that will destroy its thread after the given
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* number of milliseconds.
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*/
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LazyIdleThread(uint32_t aIdleTimeoutMS,
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const nsCSubstring& aName,
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ShutdownMethod aShutdownMethod = AutomaticShutdown,
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nsIObserver* aIdleObserver = nullptr);
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/**
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* Add an observer that will be notified when the thread is idle and about to
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* be shut down. The aSubject argument can be QueryInterface'd to an nsIThread
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* that can be used to post cleanup events. The aTopic argument will be
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* IDLE_THREAD_TOPIC, and aData will be null. The LazyIdleThread does not add
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* a reference to the observer to avoid circular references as it is assumed
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* to be the owner. It is the caller's responsibility to clear this observer
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* if the pointer becomes invalid.
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*/
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void SetWeakIdleObserver(nsIObserver* aObserver);
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/**
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* Disable the idle timeout for this thread. No effect if the timeout is
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* already disabled.
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*/
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void DisableIdleTimeout();
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/**
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* Enable the idle timeout. No effect if the timeout is already enabled.
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*/
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void EnableIdleTimeout();
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private:
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/**
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* Calls Shutdown().
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*/
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~LazyIdleThread();
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/**
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* Called just before dispatching to mThread.
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*/
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void PreDispatch();
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/**
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* Makes sure a valid thread lives in mThread.
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*/
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nsresult EnsureThread();
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/**
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* Called on mThread to set up the thread observer.
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*/
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void InitThread();
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/**
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* Called on mThread to clean up the thread observer.
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*/
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void CleanupThread();
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/**
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* Called on the main thread when mThread believes itself to be idle. Sets up
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* the idle timer.
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*/
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void ScheduleTimer();
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/**
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* Called when we are shutting down mThread.
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*/
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nsresult ShutdownThread();
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/**
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* Deletes this object. Used to delay calling mThread->Shutdown() during the
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* final release (during a GC, for instance).
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*/
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void SelfDestruct();
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/**
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* Returns true if events should be queued rather than immediately dispatched
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* to mThread. Currently only happens when the thread is shutting down.
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*/
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bool UseRunnableQueue()
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{
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return !!mQueuedRunnables;
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}
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/**
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* Protects data that is accessed on both threads.
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*/
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mozilla::Mutex mMutex;
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/**
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* Touched on both threads but set before mThread is created. Used to direct
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* timer events to the owning thread.
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*/
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nsCOMPtr<nsIThread> mOwningThread;
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/**
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* Only accessed on the owning thread. Set by EnsureThread().
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*/
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nsCOMPtr<nsIThread> mThread;
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/**
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* Protected by mMutex. Created when mThread has no pending events and fired
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* at mOwningThread. Any thread that dispatches to mThread will take ownership
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* of the timer and fire a separate cancel event to the owning thread.
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*/
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nsCOMPtr<nsITimer> mIdleTimer;
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/**
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* Idle observer. Called when the thread is about to be shut down. Released
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* only when Shutdown() is called.
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*/
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nsIObserver* MOZ_UNSAFE_REF("See the documentation for SetWeakIdleObserver for "
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"how the owner of LazyIdleThread should manage the "
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"lifetime information of this field") mIdleObserver;
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/**
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* Temporary storage for events that happen to be dispatched while we're in
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* the process of shutting down our real thread.
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*/
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nsTArray<nsCOMPtr<nsIRunnable>>* mQueuedRunnables;
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/**
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* The number of milliseconds a thread should be idle before dying.
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*/
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const uint32_t mIdleTimeoutMS;
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/**
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* The number of events that are pending on mThread. A nonzero value means
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* that the thread cannot be cleaned up.
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*/
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uint32_t mPendingEventCount;
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/**
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* The number of times that mThread has dispatched an idle notification. Any
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* timer that fires while this count is nonzero can safely be ignored as
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* another timer will be on the way.
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*/
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uint32_t mIdleNotificationCount;
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/**
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* Whether or not the thread should automatically shutdown. If the owner
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* specified ManualShutdown at construction time then the owner should take
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* care to call Shutdown() manually when appropriate.
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*/
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ShutdownMethod mShutdownMethod;
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/**
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* Only accessed on the owning thread. Set to true when Shutdown() has been
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* called and prevents EnsureThread() from recreating mThread.
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*/
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bool mShutdown;
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/**
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* Set from CleanupThread and lasting until the thread has shut down. Prevents
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* further idle notifications during the shutdown process.
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*/
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bool mThreadIsShuttingDown;
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/**
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* Whether or not the idle timeout is enabled.
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*/
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bool mIdleTimeoutEnabled;
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/**
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* Name of the thread, set on the actual thread after it gets created.
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*/
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nsCString mName;
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};
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} // namespace mozilla
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#endif // mozilla_lazyidlethread_h__
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