Speculative patch: Make it safe to delete the TQM inside a Task

content/child/scheduler/task_queue_manager.h

Index: content/child/scheduler/task_queue_manager.h
diff --git a/content/child/scheduler/task_queue_manager.h b/content/child/scheduler/task_queue_manager.h
index e8563ee6fd1bf369e9ba180383a388f91dd72eda..1f91073026844cf378d87835098ed3efe6eae3c4 100644
--- a/content/child/scheduler/task_queue_manager.h
+++ b/content/child/scheduler/task_queue_manager.h
@@ -128,6 +128,12 @@ class CONTENT_EXPORT TaskQueueManager {
   friend class internal::LazyNow;
   friend class internal::TaskQueue;
 
+  class DeletionSentinel : public base::RefCounted<DeletionSentinel> {
+   private:
+    friend class base::RefCounted<DeletionSentinel>;
+    ~DeletionSentinel() {}
+  };
+
   // Called by the task queue to register a new pending task and allocate a
   // sequence number for it.
   void DidQueueTask(base::PendingTask* pending_task);
@@ -198,6 +204,7 @@ class CONTENT_EXPORT TaskQueueManager {
 
   const char* disabled_by_default_tracing_category_;
 
+  scoped_refptr<DeletionSentinel> deletion_sentinel_;
   base::WeakPtrFactory<TaskQueueManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TaskQueueManager);