Correctly handle the case when TimerTask is destroyed with being run.

src/heap/memory-reducer.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/memory-reducer.h"
 
 #include "src/flags.h"
 #include "src/heap/heap.h"
 #include "src/utils.h"
 #include "src/v8.h"
@@ skipping 159 matching lines @@
   // 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);
   V8::GetCurrentPlatform()->CallDelayedOnForegroundThread(
       isolate, pending_task_, (delay_ms + kSlackMs) / 1000.0);
 }
 
 
+void MemoryReducer::ClearTask(v8::Task* task) {
+  if (pending_task_ == task) {
+    pending_task_ = nullptr;
+  }
+}
+
+
 void MemoryReducer::TearDown() {
   if (pending_task_ != nullptr) {
     pending_task_->NotifyHeapTearDown();
     pending_task_ = nullptr;
   }
   state_ = State(kDone, 0, 0);
 }
 
 }  // internal
 }  // v8