Add {CancelableTaskManager} to handle {Cancelable} concurrent tasks.

src/heap/scavenge-job.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/scavenge-job.h"
 
 #include "src/base/platform/time.h"
 #include "src/heap/heap-inl.h"
 #include "src/heap/heap.h"
 #include "src/isolate.h"
 #include "src/v8.h"
 
 namespace v8 {
 namespace internal {
 
 
 const double ScavengeJob::kMaxAllocationLimitAsFractionOfNewSpace = 0.8;
 
 void ScavengeJob::IdleTask::RunInternal(double deadline_in_seconds) {
-  Heap* heap = isolate_->heap();
+  Heap* heap = isolate()->heap();
   double deadline_in_ms =
       deadline_in_seconds *
       static_cast<double>(base::Time::kMillisecondsPerSecond);
   double start_ms = heap->MonotonicallyIncreasingTimeInMs();
   double idle_time_in_ms = deadline_in_ms - start_ms;
   size_t scavenge_speed_in_bytes_per_ms =
       static_cast<size_t>(heap->tracer()->ScavengeSpeedInBytesPerMillisecond());
   size_t new_space_size = heap->new_space()->Size();
   size_t new_space_capacity = heap->new_space()->Capacity();
 
@@ skipping 76 matching lines @@
     v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(heap->isolate());
     if (V8::GetCurrentPlatform()->IdleTasksEnabled(isolate)) {
       idle_task_pending_ = true;
       auto task = new IdleTask(heap->isolate(), this);
       V8::GetCurrentPlatform()->CallIdleOnForegroundThread(isolate, task);
     }
   }
 }
 }  // namespace internal
 }  // namespace v8