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

trunk/src/base/message_loop/message_pump_mac.mm

 // 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.
 
 #import "base/message_loop/message_pump_mac.h"
 
 #import <Foundation/Foundation.h>
 
 #include <limits>
 
@@ skipping 598 matching lines @@
                                        context:NULL
                                        subtype:0
                                          data1:0
                                          data2:0]
            atStart:NO];
 }
 
 MessagePumpCrApplication::MessagePumpCrApplication() {
 }
 
-MessagePumpCrApplication::~MessagePumpCrApplication() {
-}
-
 // Prevents an autorelease pool from being created if the app is in the midst of
 // handling a UI event because various parts of AppKit depend on objects that
 // are created while handling a UI event to be autoreleased in the event loop.
 // An example of this is NSWindowController. When a window with a window
 // controller is closed it goes through a stack like this:
 // (Several stack frames elided for clarity)
 //
 // #0 [NSWindowController autorelease]
 // #1 DoAClose
 // #2 MessagePumpCFRunLoopBase::DoWork()
@@ skipping 63 matching lines @@
     [NSApplication sharedApplication];
     g_not_using_cr_app = true;
     return new MessagePumpNSApplication;
 #endif
   }
 
   return new MessagePumpNSRunLoop;
 }
 
 }  // namespace base