mus: Fix handled status in UI event ack, add MessageLoop::NestingObserver

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 115 matching lines @@
 
   typedef std::unique_ptr<MessagePump>(MessagePumpFactory)();
   // Uses the given base::MessagePumpForUIFactory to override the default
   // MessagePump implementation for 'TYPE_UI'. Returns true if the factory
   // was successfully registered.
   static bool InitMessagePumpForUIFactory(MessagePumpFactory* factory);
 
   // Creates the default MessagePump based on |type|. Caller owns return
   // value.
   static std::unique_ptr<MessagePump> CreateMessagePumpForType(Type type);
+
   // A DestructionObserver is notified when the current MessageLoop is being
   // destroyed.  These observers are notified prior to MessageLoop::current()
   // being changed to return NULL.  This gives interested parties the chance to
   // do final cleanup that depends on the MessageLoop.
   //
   // NOTE: Any tasks posted to the MessageLoop during this notification will
   // not be run.  Instead, they will be deleted.
   //
   class BASE_EXPORT DestructionObserver {
    public:
     virtual void WillDestroyCurrentMessageLoop() = 0;
 
    protected:
     virtual ~DestructionObserver();
   };
 
   // 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);
+
   // NOTE: Deprecated; prefer task_runner() and the TaskRunner interfaces.
   // TODO(skyostil): Remove these functions (crbug.com/465354).
   //
   // The "PostTask" family of methods call the task's Run method asynchronously
   // from within a message loop at some point in the future.
   //
   // With the PostTask variant, tasks are invoked in FIFO order, inter-mixed
   // with normal UI or IO event processing.  With the PostDelayedTask variant,
   // tasks are called after at least approximately 'delay_ms' have elapsed.
   //
@@ skipping 296 matching lines @@
 
   // Start recording histogram info about events and action IF it was enabled
   // and IF the statistics recorder can accept a registration of our histogram.
   void StartHistogrammer();
 
   // Add occurrence of event to our histogram, so that we can see what is being
   // done in a specific MessageLoop instance (i.e., specific thread).
   // If message_histogram_ is NULL, this is a no-op.
   void HistogramEvent(int event);
 
+  // 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_;
 
 #if defined(OS_WIN)
   // Should be set to true before calling Windows APIs like TrackPopupMenu, etc.
   // which enter a modal message loop.
   bool os_modal_loop_;
 #endif
 
@@ skipping 171 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_