Revert of Revert "[Mac] Reland r276808 Use a native MessagePump instead of a MessagePumpDefault"

base/message_loop/message_pump_default.h

 // Copyright (c) 2012 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_PUMP_DEFAULT_H_
 #define BASE_MESSAGE_LOOP_MESSAGE_PUMP_DEFAULT_H_
 
+#include "base/base_export.h"
 #include "base/message_loop/message_pump.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/time/time.h"
 
 namespace base {
 
-class MessagePumpDefault : public MessagePump {
+class BASE_EXPORT MessagePumpDefault : public MessagePump {
  public:
   MessagePumpDefault();
   virtual ~MessagePumpDefault();
 
   // MessagePump methods:
   virtual void Run(Delegate* delegate) OVERRIDE;
   virtual void Quit() OVERRIDE;
   virtual void ScheduleWork() OVERRIDE;
   virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time) OVERRIDE;
 
  private:
   // This flag is set to false when Run should return.
   bool keep_running_;
 
   // Used to sleep until there is more work to do.
   WaitableEvent event_;
 
   // The time at which we should call DoDelayedWork.
   TimeTicks delayed_work_time_;
 
   DISALLOW_COPY_AND_ASSIGN(MessagePumpDefault);
 };
 
 }  // namespace base
 
 #endif  // BASE__MESSAGE_LOOPMESSAGE_PUMP_DEFAULT_H_