Reland "Use background tasks for the compiler dispatcher

src/cancelable-task.h

 // 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.
 
 #ifndef V8_CANCELABLE_TASK_H_
 #define V8_CANCELABLE_TASK_H_
 
 #include <map>
 
 #include "include/v8-platform.h"
@@ skipping 108 matching lines @@
   friend class CancelableTaskManager;
 
   DISALLOW_COPY_AND_ASSIGN(Cancelable);
 };
 
 
 // Multiple inheritance can be used because Task is a pure interface.
 class CancelableTask : public Cancelable, public Task {
  public:
   explicit CancelableTask(Isolate* isolate);
+  CancelableTask(Isolate* isolate, CancelableTaskManager* manager);
 
   // Task overrides.
   void Run() final {
     if (TryRun()) {
       RunInternal();
     }
   }
 
   virtual void RunInternal() = 0;
 
   Isolate* isolate() { return isolate_; }
 
  private:
   Isolate* isolate_;
   DISALLOW_COPY_AND_ASSIGN(CancelableTask);
 };
 
 
 // Multiple inheritance can be used because IdleTask is a pure interface.
 class CancelableIdleTask : public Cancelable, public IdleTask {
  public:
   explicit CancelableIdleTask(Isolate* isolate);
+  CancelableIdleTask(Isolate* isolate, CancelableTaskManager* manager);
 
   // IdleTask overrides.
   void Run(double deadline_in_seconds) final {
     if (TryRun()) {
       RunInternal(deadline_in_seconds);
     }
   }
 
   virtual void RunInternal(double deadline_in_seconds) = 0;
 
   Isolate* isolate() { return isolate_; }
 
  private:
   Isolate* isolate_;
   DISALLOW_COPY_AND_ASSIGN(CancelableIdleTask);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CANCELABLE_TASK_H_