[Reland] Make canceling Timers fast.

third_party/WebKit/Source/platform/Timer.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 18 matching lines @@
 #include "platform/PlatformExport.h"
 #include "platform/heap/Handle.h"
 #include "public/platform/WebTaskRunner.h"
 #include "public/platform/WebTraceLocation.h"
 #include "wtf/AddressSanitizer.h"
 #include "wtf/Allocator.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/Threading.h"
 #include "wtf/Vector.h"
+#include "wtf/WeakPtr.h"
 
 namespace blink {
 
 // Time intervals are all in seconds.
 
 class PLATFORM_EXPORT TimerBase {
     WTF_MAKE_NONCOPYABLE(TimerBase);
 public:
     explicit TimerBase(WebTaskRunner*);
     virtual ~TimerBase();
 
     void start(double nextFireInterval, double repeatInterval, const WebTraceLocation&);
 
     void startRepeating(double repeatInterval, const WebTraceLocation& caller)
     {
         start(repeatInterval, repeatInterval, caller);
     }
     void startOneShot(double interval, const WebTraceLocation& caller)
     {
         start(interval, 0, caller);
     }
 
-    // Timer cancellation is supported but not free. Please be careful not to
-    // cause a flood of timer cancellations.
+    // Timer cancellation is fast enough that you shouldn't have to worry
+    // about it unless you're canceling tens of thousands of tasks.
     void stop();
     bool isActive() const;
     const WebTraceLocation& location() const { return m_location; }
 
     double nextFireInterval() const;
     double repeatInterval() const { return m_repeatInterval; }
 
     void augmentRepeatInterval(double delta) {
         double now = timerMonotonicallyIncreasingTime();
         setNextFireTime(now, std::max(m_nextFireTime - now + delta, 0.0));
@@ skipping 15 matching lines @@
 
     NO_LAZY_SWEEP_SANITIZE_ADDRESS
     virtual bool canFire() const { return true; }
 
     double timerMonotonicallyIncreasingTime() const;
 
     void setNextFireTime(double now, double delay);
 
     void runInternal();
 
-    class CancellableTimerTask final : public WebTaskRunner::Task {
-        WTF_MAKE_NONCOPYABLE(CancellableTimerTask);
-    public:
-        explicit CancellableTimerTask(TimerBase* timer) : m_timer(timer) { }
-
-        NO_LAZY_SWEEP_SANITIZE_ADDRESS
-        ~CancellableTimerTask() override
-        {
-            if (m_timer)
-                m_timer->m_cancellableTimerTask = nullptr;
-        }
-
-        NO_LAZY_SWEEP_SANITIZE_ADDRESS
-        void run() override
-        {
-            if (m_timer) {
-                m_timer->m_cancellableTimerTask = nullptr;
-                m_timer->runInternal();
-                m_timer = nullptr;
-            }
-        }
-
-        void cancel()
-        {
-            m_timer = nullptr;
-        }
-
-    private:
-        TimerBase* m_timer; // NOT OWNED
-    };
-
     double m_nextFireTime; // 0 if inactive
     double m_repeatInterval; // 0 if not repeating
     WebTraceLocation m_location;
-    CancellableTimerTask* m_cancellableTimerTask; // NOT OWNED
     std::unique_ptr<WebTaskRunner> m_webTaskRunner;
 
 #if DCHECK_IS_ON()
     ThreadIdentifier m_thread;
 #endif
+    WTF::WeakPtrFactory<TimerBase> m_weakPtrFactory;
 
     friend class ThreadTimers;
     friend class TimerHeapLessThanFunction;
     friend class TimerHeapReference;
 };
 
 template<typename T, bool = IsGarbageCollectedType<T>::value>
 class TimerIsObjectAliveTrait {
 public:
     static bool isHeapObjectAlive(T*) { return true; }
@@ skipping 72 matching lines @@
     UnthrottledThreadTimer(TimerFiredClass* timerFiredClass, TimerFiredFunction timerFiredFunction)
         : TaskRunnerTimer<TimerFiredClass>(TimerBase::getUnthrottledTaskRunner(), timerFiredClass, timerFiredFunction)
     {
     }
 };
 
 NO_LAZY_SWEEP_SANITIZE_ADDRESS
 inline bool TimerBase::isActive() const
 {
     ASSERT(m_thread == currentThread());
-    return m_cancellableTimerTask;
+    return m_weakPtrFactory.hasWeakPtrs();
 }
 
 } // namespace blink
 
 #endif // Timer_h