Don't run the second pass of the pending phantom callbacks if the heap has been torn down.

src/heap/memory-reducer.cc

Index: src/heap/memory-reducer.cc
diff --git a/src/heap/memory-reducer.cc b/src/heap/memory-reducer.cc
index c89d1424e7c5e78e303ae64b7043669571bb4035..be4b43f535aa64fd5a24b34eba6f32087ff2f748 100644
--- a/src/heap/memory-reducer.cc
+++ b/src/heap/memory-reducer.cc
@@ -16,9 +16,12 @@ const int MemoryReducer::kLongDelayMs = 5000;
 const int MemoryReducer::kShortDelayMs = 500;
 const int MemoryReducer::kMaxNumberOfGCs = 3;
 
+MemoryReducer::TimerTask::TimerTask(MemoryReducer* memory_reducer)
+    : CancelableTask(memory_reducer->heap()->isolate()),
+      memory_reducer_(memory_reducer) {}
 
-void MemoryReducer::TimerTask::Run() {
-  if (heap_is_torn_down_) return;
+
+void MemoryReducer::TimerTask::RunInternal() {
   Heap* heap = memory_reducer_->heap();
   Event event;
   event.type = kTimer;
@@ -32,10 +35,8 @@ void MemoryReducer::TimerTask::Run() {
 
 
 void MemoryReducer::NotifyTimer(const Event& event) {
-  DCHECK(nullptr != pending_task_);
   DCHECK_EQ(kTimer, event.type);
   DCHECK_EQ(kWait, state_.action);
-  pending_task_ = nullptr;
   state_ = Step(state_, event);
   if (state_.action == kRun) {
     DCHECK(heap()->incremental_marking()->IsStopped());
@@ -170,25 +171,13 @@ void MemoryReducer::ScheduleTimer(double delay_ms) {
   // Leave some room for precision error in task scheduler.
   const double kSlackMs = 100;
   v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(heap()->isolate());
-  DCHECK(nullptr == pending_task_);
-  pending_task_ = new MemoryReducer::TimerTask(this);
+  auto timer_task = new MemoryReducer::TimerTask(this);
   V8::GetCurrentPlatform()->CallDelayedOnForegroundThread(
-      isolate, pending_task_, (delay_ms + kSlackMs) / 1000.0);
-}
-
-
-void MemoryReducer::ClearTask(v8::Task* task) {
-  if (pending_task_ == task) {
-    pending_task_ = nullptr;
-  }
+      isolate, timer_task, (delay_ms + kSlackMs) / 1000.0);
 }
 
 
 void MemoryReducer::TearDown() {
-  if (pending_task_ != nullptr) {
-    pending_task_->NotifyHeapTearDown();
-    pending_task_ = nullptr;
-  }
   state_ = State(kDone, 0, 0);
 }