base::RefCounted now DCHECKs when referenced from multiple threads.

ipc/ipc_message_attachment.h

 // Copyright (c) 2015 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 IPC_IPC_MESSAGE_ATTACHMENT_H_
 #define IPC_IPC_MESSAGE_ATTACHMENT_H_
 
 #include "base/files/file.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "ipc/ipc_export.h"
 
 namespace IPC {
 
 // Auxiliary data sent with |Message|. This can be a platform file descriptor
 // or a mojo |MessagePipe|. |GetType()| returns the type of the subclass.
+// TODO(mgiuca): Avoid using UnsafeRefCounted. http://crbug.com/469952.
 class IPC_EXPORT MessageAttachment
-    : public base::RefCounted<MessageAttachment> {
+    : public base::UnsafeRefCounted<MessageAttachment> {
  public:
   enum Type {
     TYPE_PLATFORM_FILE,  // The instance is |PlatformFileAttachment|.
     TYPE_MOJO_HANDLE,    // The instance is |MojoHandleAttachment|.
   };
 
   virtual Type GetType() const = 0;
 
 #if defined(OS_POSIX)
   virtual base::PlatformFile TakePlatformFile() = 0;
 #endif  // OS_POSIX
 
  protected:
-  friend class base::RefCounted<MessageAttachment>;
+  friend class base::UnsafeRefCounted<MessageAttachment>;
   MessageAttachment();
   virtual ~MessageAttachment();
 
   DISALLOW_COPY_AND_ASSIGN(MessageAttachment);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_MESSAGE_ATTACHMENT_H_