RefCounted types should not have public destructors, delegate cleanup

content/common/gpu/gpu_command_buffer_stub.h

 // 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.
 
 #ifndef CONTENT_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_
 #define CONTENT_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_
 #pragma once
 
 #if defined(ENABLE_GPU)
 
@@ skipping 66 matching lines @@
 };
 
 class GpuCommandBufferStub
     : public GpuCommandBufferStubBase,
       public IPC::Channel::Listener,
       public IPC::Message::Sender,
       public base::SupportsWeakPtr<GpuCommandBufferStub> {
  public:
   class DestructionObserver {
    public:
-    ~DestructionObserver() {}
-
     // Called in Destroy(), before the context/surface are released.
     virtual void OnWillDestroyStub(GpuCommandBufferStub* stub) = 0;
+
+   protected:
+    virtual ~DestructionObserver() {}
   };
 
   GpuCommandBufferStub(
       GpuChannel* channel,
       GpuCommandBufferStub* share_group,
       const gfx::GLSurfaceHandle& handle,
       gpu::gles2::MailboxManager* mailbox_manager,
       const gfx::Size& size,
       const gpu::gles2::DisallowedFeatures& disallowed_features,
       const std::string& allowed_extensions,
@@ skipping 153 matching lines @@
   IDMap<GpuVideoDecodeAccelerator, IDMapOwnPointer> video_decoders_;
 
   ObserverList<DestructionObserver> destruction_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuCommandBufferStub);
 };
 
 #endif  // defined(ENABLE_GPU)
 
 #endif  // CONTENT_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_