Made MessagePump a non-thread safe class.

base/message_loop/message_pump_default.h

Index: base/message_loop/message_pump_default.h
diff --git a/base/message_loop/message_pump_default.h b/base/message_loop/message_pump_default.h
index 07a6c704c68dfd545d0f8dbc4a5be3b575f0dfbb..a9b83e8de70707e0a6972394d8bdcae9f00db0ce 100644
--- a/base/message_loop/message_pump_default.h
+++ b/base/message_loop/message_pump_default.h
@@ -14,6 +14,7 @@ namespace base {
 class MessagePumpDefault : public MessagePump {
  public:
   MessagePumpDefault();
+  virtual ~MessagePumpDefault();
 
   // MessagePump methods:
   virtual void Run(Delegate* delegate) OVERRIDE;
@@ -21,9 +22,6 @@ class MessagePumpDefault : public MessagePump {
   virtual void ScheduleWork() OVERRIDE;
   virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time) OVERRIDE;
 
- protected:
-  virtual ~MessagePumpDefault() {}
-
  private:
   // This flag is set to false when Run should return.
   bool keep_running_;