Made MessagePump a non-thread safe class.

base/message_loop/message_pump_libevent.h

Index: base/message_loop/message_pump_libevent.h
diff --git a/base/message_loop/message_pump_libevent.h b/base/message_loop/message_pump_libevent.h
index 3b1d26d4fa1ded006ab33e61e305958834d0e40c..f3a48a9f62fd40078d5ca6ce0416f4c50a19b82d 100644
--- a/base/message_loop/message_pump_libevent.h
+++ b/base/message_loop/message_pump_libevent.h
@@ -98,6 +98,7 @@ class BASE_EXPORT MessagePumpLibevent : public MessagePump {
   };
 
   MessagePumpLibevent();
+  virtual ~MessagePumpLibevent();
 
   // Have the current thread's message loop watch for a a situation in which
   // reading/writing to the FD can be performed without blocking.
@@ -126,9 +127,6 @@ class BASE_EXPORT MessagePumpLibevent : public MessagePump {
   virtual void ScheduleWork() OVERRIDE;
   virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time) OVERRIDE;
 
- protected:
-  virtual ~MessagePumpLibevent();
-
  private:
   friend class MessagePumpLibeventTest;