Use background tasks for the compiler dispatcher

src/cancelable-task.cc

Index: src/cancelable-task.cc
diff --git a/src/cancelable-task.cc b/src/cancelable-task.cc
index ea351f8908ce3694382ce1c597c4f46d2f81fb7e..b712d98877ce930946bd8ceb4754bf4fe403ef8f 100644
--- a/src/cancelable-task.cc
+++ b/src/cancelable-task.cc
@@ -93,13 +93,18 @@ void CancelableTaskManager::CancelAndWait() {
   }
 }
 
-
 CancelableTask::CancelableTask(Isolate* isolate)
-    : Cancelable(isolate->cancelable_task_manager()), isolate_(isolate) {}
+    : CancelableTask(isolate, isolate->cancelable_task_manager()) {}
 
+CancelableTask::CancelableTask(Isolate* isolate, CancelableTaskManager* manager)
+    : Cancelable(manager), isolate_(isolate) {}
 
 CancelableIdleTask::CancelableIdleTask(Isolate* isolate)
-    : Cancelable(isolate->cancelable_task_manager()), isolate_(isolate) {}
+    : CancelableIdleTask(isolate, isolate->cancelable_task_manager()) {}
+
+CancelableIdleTask::CancelableIdleTask(Isolate* isolate,
+                                       CancelableTaskManager* manager)
+    : Cancelable(manager), isolate_(isolate) {}
 
 }  // namespace internal
 }  // namespace v8