Revert of Use background tasks for the compiler dispatcher

src/cancelable-task.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/cancelable-task.h"
 
 #include "src/base/platform/platform.h"
 #include "src/isolate.h"
 
 namespace v8 {
@@ skipping 75 matching lines @@
         cancelable_tasks_.erase(current);
       }
     }
     // Wait for already running background tasks.
     if (!cancelable_tasks_.empty()) {
       cancelable_tasks_barrier_.Wait(&mutex_);
     }
   }
 }
 
+
 CancelableTask::CancelableTask(Isolate* isolate)
-    : CancelableTask(isolate, isolate->cancelable_task_manager()) {}
+    : Cancelable(isolate->cancelable_task_manager()), isolate_(isolate) {}
 
-CancelableTask::CancelableTask(Isolate* isolate, CancelableTaskManager* manager)
-    : Cancelable(manager), isolate_(isolate) {}
 
 CancelableIdleTask::CancelableIdleTask(Isolate* isolate)
-    : CancelableIdleTask(isolate, isolate->cancelable_task_manager()) {}
-
-CancelableIdleTask::CancelableIdleTask(Isolate* isolate,
-                                       CancelableTaskManager* manager)
-    : Cancelable(manager), isolate_(isolate) {}
+    : Cancelable(isolate->cancelable_task_manager()), isolate_(isolate) {}
 
 }  // namespace internal
 }  // namespace v8