Revert 212948 "Made MessagePump a non-thread safe class."

trunk/src/base/message_loop/message_pump_libevent.h

Index: trunk/src/base/message_loop/message_pump_libevent.h
===================================================================
--- trunk/src/base/message_loop/message_pump_libevent.h	(revision 212951)
+++ trunk/src/base/message_loop/message_pump_libevent.h	(working copy)
@@ -98,7 +98,6 @@
   };
 
   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.
@@ -127,6 +126,9 @@
   virtual void ScheduleWork() OVERRIDE;
   virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time) OVERRIDE;
 
+ protected:
+  virtual ~MessagePumpLibevent();
+
  private:
   friend class MessagePumpLibeventTest;