Make nesting/running states a RunLoop rather than a MessageLoop concept.

base/message_loop/message_loop.h

 // Copyright 2013 The Chromium 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 BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_
 #define BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_
 
 #include <memory>
 #include <queue>
 #include <string>
@@ skipping 144 matching lines @@
   };
 
   // Add a DestructionObserver, which will start receiving notifications
   // immediately.
   void AddDestructionObserver(DestructionObserver* destruction_observer);
 
   // Remove a DestructionObserver.  It is safe to call this method while a
   // DestructionObserver is receiving a notification callback.
   void RemoveDestructionObserver(DestructionObserver* destruction_observer);
 
-  // A NestingObserver is notified when a nested message loop begins. The
-  // observers are notified before the first task is processed.
-  class BASE_EXPORT NestingObserver {
-   public:
-    virtual void OnBeginNestedMessageLoop() = 0;
-
-   protected:
-    virtual ~NestingObserver();
-  };
-
-  void AddNestingObserver(NestingObserver* observer);
-  void RemoveNestingObserver(NestingObserver* observer);
-
   // Deprecated: use RunLoop instead.
   //
   // Signals the Run method to return when it becomes idle. It will continue to
   // process pending messages and future messages as long as they are enqueued.
   // Warning: if the MessageLoop remains busy, it may never quit. Only use this
   // Quit method when looping procedures (such as web pages) have been shut
   // down.
   //
   // This method may only be called on the same thread that called Run, and Run
   // must still be on the call stack.
@@ skipping 82 matching lines @@
     }
     ~ScopedNestableTaskAllower() {
       loop_->SetNestableTasksAllowed(old_state_);
     }
 
    private:
     MessageLoop* loop_;
     bool old_state_;
   };
 
-  // Returns true if we are currently running a nested message loop.
-  bool IsNested();
-
   // A TaskObserver is an object that receives task notifications from the
   // MessageLoop.
   //
   // NOTE: A TaskObserver implementation should be extremely fast!
   class BASE_EXPORT TaskObserver {
    public:
     TaskObserver();
 
     // This method is called before processing a task.
     virtual void WillProcessTask(const PendingTask& pending_task) = 0;
 
     // This method is called after processing a task.
     virtual void DidProcessTask(const PendingTask& pending_task) = 0;
 
    protected:
     virtual ~TaskObserver();
   };
 
   // These functions can only be called on the same thread that |this| is
   // running on.
   void AddTaskObserver(TaskObserver* task_observer);
   void RemoveTaskObserver(TaskObserver* task_observer);
 
-  // Can only be called from the thread that owns the MessageLoop.
-  bool is_running() const;
-
   // Returns true if the message loop has high resolution timers enabled.
   // Provided for testing.
   bool HasHighResolutionTasks();
 
   // Returns true if the message loop is "idle". Provided for testing.
   bool IsIdleForTesting();
 
   // Returns the TaskAnnotator which is used to add debug information to posted
   // tasks.
   debug::TaskAnnotator* task_annotator() { return &task_annotator_; }
 
   // Runs the specified PendingTask.
   void RunTask(PendingTask* pending_task);
 
-  bool nesting_allowed() const { return allow_nesting_; }
-
-  // Disallow nesting. After this is called, running a nested RunLoop or calling
-  // Add/RemoveNestingObserver() on this MessageLoop will crash.
-  void DisallowNesting() { allow_nesting_ = false; }
-
   // Disallow task observers. After this is called, calling
   // Add/RemoveTaskObserver() on this MessageLoop will crash.
   void DisallowTaskObservers() { allow_task_observers_ = false; }
 
   //----------------------------------------------------------------------------
  protected:
   std::unique_ptr<MessagePump> pump_;
 
   using MessagePumpFactoryCallback = Callback<std::unique_ptr<MessagePump>()>;
 
@@ skipping 55 matching lines @@
   bool DeletePendingTasks();
 
   // Loads tasks from the incoming queue to |work_queue_| if the latter is
   // empty.
   void ReloadWorkQueue();
 
   // Wakes up the message pump. Can be called on any thread. The caller is
   // responsible for synchronizing ScheduleWork() calls.
   void ScheduleWork();
 
-  // Notify observers that a nested message loop is starting.
-  void NotifyBeginNestedLoop();
-
   // MessagePump::Delegate methods:
   bool DoWork() override;
   bool DoDelayedWork(TimeTicks* next_delayed_work_time) override;
   bool DoIdleWork() override;
 
   const Type type_;
 
   // A list of tasks that need to be processed by this instance.  Note that
   // this queue is only accessed (push/pop) by our current thread.
   TaskQueue work_queue_;
@@ skipping 14 matching lines @@
   // A recent snapshot of Time::Now(), used to check delayed_work_queue_.
   TimeTicks recent_time_;
 
   // A queue of non-nestable tasks that we had to defer because when it came
   // time to execute them we were in a nested message loop.  They will execute
   // once we're out of nested message loops.
   TaskQueue deferred_non_nestable_work_queue_;
 
   ObserverList<DestructionObserver> destruction_observers_;
 
-  ObserverList<NestingObserver> nesting_observers_;
-
   // A recursion block that prevents accidentally running additional tasks when
   // insider a (accidentally induced?) nested message pump.
   bool nestable_tasks_allowed_;
 
   // pump_factory_.Run() is called to create a message pump for this loop
   // if type_ is TYPE_CUSTOM and pump_ is null.
   MessagePumpFactoryCallback pump_factory_;
 
   RunLoop* run_loop_;
 
@@ skipping 14 matching lines @@
   scoped_refptr<internal::MessageLoopTaskRunner> unbound_task_runner_;
 
   // The task runner associated with this message loop.
   scoped_refptr<SingleThreadTaskRunner> task_runner_;
   std::unique_ptr<ThreadTaskRunnerHandle> thread_task_runner_handle_;
 
   // Id of the thread this message loop is bound to. Initialized once when the
   // MessageLoop is bound to its thread and constant forever after.
   PlatformThreadId thread_id_;
 
-  // Whether nesting is allowed.
-  bool allow_nesting_ = true;
+  // Whether this MessageLoop is currently running in nested RunLoops.
+  bool is_nested_ = false;
 
   // Whether task observers are allowed.
   bool allow_task_observers_ = true;
 
   DISALLOW_COPY_AND_ASSIGN(MessageLoop);
 };
 
 #if !defined(OS_NACL)
 
 //-----------------------------------------------------------------------------
@@ skipping 131 matching lines @@
 
 // Do not add any member variables to MessageLoopForIO!  This is important b/c
 // MessageLoopForIO is often allocated via MessageLoop(TYPE_IO).  Any extra
 // data that you need should be stored on the MessageLoop's pump_ instance.
 static_assert(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
               "MessageLoopForIO should not have extra member variables");
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_