Revert of Make canceling Timers fast.

third_party/WebKit/Source/platform/Timer.h

Index: third_party/WebKit/Source/platform/Timer.h
diff --git a/third_party/WebKit/Source/platform/Timer.h b/third_party/WebKit/Source/platform/Timer.h
index 1a1b6f60001b496f95995f03ae92f241a2302d14..6269416f8e85f0a0b4ded5f5c8cee0b5f70bd47a 100644
--- a/third_party/WebKit/Source/platform/Timer.h
+++ b/third_party/WebKit/Source/platform/Timer.h
@@ -36,7 +36,6 @@
 #include "wtf/Noncopyable.h"
 #include "wtf/Threading.h"
 #include "wtf/Vector.h"
-#include "wtf/WeakPtr.h"
 
 namespace blink {
 
@@ -59,8 +58,8 @@
         start(interval, 0, caller);
     }
 
-    // Timer cancellation is fast enough that you shouldn't have to worry
-    // about it unless you're canceling tens of thousands of tasks.
+    // Timer cancellation is supported but not free. Please be careful not to
+    // cause a flood of timer cancellations.
     void stop();
     bool isActive() const;
     const WebTraceLocation& location() const { return m_location; }
@@ -96,15 +95,46 @@
 
     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;
@@ -197,7 +227,7 @@
 inline bool TimerBase::isActive() const
 {
     ASSERT(m_thread == currentThread());
-    return m_weakPtrFactory.hasWeakPtrs();
+    return m_cancellableTimerTask;
 }
 
 } // namespace blink