Add undeclared virtual destructors part 2...

chrome/common/mach_message_source_mac.h

 // Copyright (c) 2008 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 CHROME_COMMON_MACH_MESSAGE_SOURCE_MAC_H_
 #define CHROME_COMMON_MACH_MESSAGE_SOURCE_MAC_H_
 
 #include <CoreServices/CoreServices.h>
 
 #include "base/scoped_cftyperef.h"
@@ skipping 20 matching lines @@
 //
 //  CFRunLoopRun();  // Process messages on runloop...
 class MachMessageSource {
  public:
   // Classes that want to listen on a Mach port can implement
   // OnMachMessageReceived, |mach_msg| is a pointer to the raw message data and
   // |size| is the buffer size;
   class MachPortListener {
    public:
     virtual void OnMachMessageReceived(void* mach_msg, size_t size) = 0;
+
+   protected:
+    virtual ~OnMachMessageReceived() {}
   };
 
   // |listener| is a week reference passed to CF, it needs to remain in
   // existence till this object is destroeyd.
   MachMessageSource(mach_port_t port,
                     MachPortListener* listener,
                     bool* success);
   ~MachMessageSource();
 
  private:
   // Called by CF when a new message arrives on the Mach port.
   static void OnReceiveMachMessage(CFMachPortRef port, void* msg, CFIndex size,
                                    void* closure);
 
   scoped_cftyperef<CFRunLoopSourceRef> machport_runloop_ref_;
   DISALLOW_COPY_AND_ASSIGN(MachMessageSource);
 };
 
 #endif // CHROME_COMMON_MACH_MESSAGE_SOURCE_MAC_H_