Make idle tasks optional in the default platform.

src/libplatform/default-platform.h

 // 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.
 
 #ifndef V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
 #define V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
 
 #include <functional>
 #include <map>
 #include <memory>
 #include <queue>
 #include <vector>
 
 #include "include/libplatform/libplatform-export.h"
+#include "include/libplatform/libplatform.h"
 #include "include/libplatform/v8-tracing.h"
 #include "include/v8-platform.h"
 #include "src/base/compiler-specific.h"
 #include "src/base/macros.h"
 #include "src/base/platform/mutex.h"
 #include "src/libplatform/task-queue.h"
 
 namespace v8 {
 namespace platform {
 
 class TaskQueue;
 class Thread;
 class WorkerThread;
 
 namespace tracing {
 class TracingController;
 }
 
 class V8_PLATFORM_EXPORT DefaultPlatform : public NON_EXPORTED_BASE(Platform) {
  public:
-  DefaultPlatform();
+  explicit DefaultPlatform(
+      IdleTaskSupport idle_task_support = IdleTaskSupport::kDisabled);
   virtual ~DefaultPlatform();
 
   void SetThreadPoolSize(int thread_pool_size);
 
   void EnsureInitialized();
 
   bool PumpMessageLoop(v8::Isolate* isolate);
 
   void RunIdleTasks(v8::Isolate* isolate, double idle_time_in_seconds);
 
@@ skipping 28 matching lines @@
  private:
   static const int kMaxThreadPoolSize;
 
   Task* PopTaskInMainThreadQueue(v8::Isolate* isolate);
   Task* PopTaskInMainThreadDelayedQueue(v8::Isolate* isolate);
   IdleTask* PopTaskInMainThreadIdleQueue(v8::Isolate* isolate);
 
   base::Mutex lock_;
   bool initialized_;
   int thread_pool_size_;
+  IdleTaskSupport idle_task_support_;
   std::vector<WorkerThread*> thread_pool_;
   TaskQueue queue_;
   std::map<v8::Isolate*, std::queue<Task*>> main_thread_queue_;
   std::map<v8::Isolate*, std::queue<IdleTask*>> main_thread_idle_queue_;
 
   typedef std::pair<double, Task*> DelayedEntry;
   std::map<v8::Isolate*,
            std::priority_queue<DelayedEntry, std::vector<DelayedEntry>,
                                std::greater<DelayedEntry> > >
       main_thread_delayed_queue_;
   std::unique_ptr<tracing::TracingController> tracing_controller_;
 
   DISALLOW_COPY_AND_ASSIGN(DefaultPlatform);
 };
 
 
 }  // namespace platform
 }  // namespace v8
 
 
 #endif  // V8_LIBPLATFORM_DEFAULT_PLATFORM_H_