Drop unused includes from worker-thread.cc

src/libplatform/worker-thread.cc

 // Copyright 2013 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 "worker-thread.h"
 
-// TODO(jochen): We should have our own version of checks.h.
-#include "../checks.h"
 #include "../../include/v8-platform.h"
 #include "task-queue.h"
 
 namespace v8 {
 namespace internal {
 
 WorkerThread::WorkerThread(TaskQueue* queue)
     : Thread("V8 WorkerThread"), queue_(queue) {
   Start();
 }
 
 
 WorkerThread::~WorkerThread() {
   Join();
 }
 
 
 void WorkerThread::Run() {
   while (Task* task = queue_->GetNext()) {
     task->Run();
     delete task;
   }
 }
 
 } }  // namespace v8::internal