Converting DomTimer from EagerSweeping to PreFinalizer

Replaced DomTimer destructor with a prefinalizer that calls Stop().
Added flag is_stopped_ to make sure second call to Stop() (from
TimerBase dtor) is noop.

Bug: 981043
Change-Id: Iab1473fe2d96fd9d6bfaf0ff2d7e46099796670f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1688928
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#675710}

third_party/blink/renderer/core/frame/dom_timer.cc

@@ -95,12 +95,16 @@ DOMTimer::DOMTimer(ExecutionContext* context,
       context, single_shot ? "setTimeout" : "setInterval", this);
 }
 
-DOMTimer::~DOMTimer() {
-  if (action_)
-    action_->Dispose();
+DOMTimer::~DOMTimer() = default;
+
+void DOMTimer::Dispose() {
+  Stop();
 }
 
 void DOMTimer::Stop() {
+  if (!action_)
+    return;
+
   const bool is_interval = !RepeatInterval().is_zero();
   probe::AsyncTaskCanceledBreakable(
       GetExecutionContext(), is_interval ? "clearInterval" : "clearTimeout",

third_party/blink/renderer/core/frame/dom_timer.h

@@ -45,6 +45,7 @@ class CORE_EXPORT DOMTimer final : public GarbageCollectedFinalized<DOMTimer>,
                                    public TimerBase,
                                    public NameClient {
   USING_GARBAGE_COLLECTED_MIXIN(DOMTimer);
+  USING_PRE_FINALIZER(DOMTimer, Dispose);
 
  public:
   // Creates a new timer owned by the ExecutionContext, starts it and returns
@@ -65,11 +66,12 @@ class CORE_EXPORT DOMTimer final : public GarbageCollectedFinalized<DOMTimer>,
   // ContextLifecycleObserver
   void ContextDestroyed(ExecutionContext*) override;
 
-  // Eager finalization is needed to promptly stop this Timer object.
+  // Pre finalizer is needed to promptly stop this Timer object.
   // Otherwise timer events might fire at an object that's slated for
   // destruction (when lazily swept), but some of its members (m_action) may
   // already have been finalized & must not be accessed.
-  EAGERLY_FINALIZE();
+  void Dispose();
+  
   void Trace(blink::Visitor*) override;
   const char* NameInHeapSnapshot() const override { return "DOMTimer"; }