[Chromoting] Implement DualBufferFrameConsumer

remoting/protocol/frame_consumer.h

 // Copyright 2016 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 REMOTING_PROTOCOL_FRAME_CONSUMER_H_
 #define REMOTING_PROTOCOL_FRAME_CONSUMER_H_
 
 #include <memory>
 
 #include "base/callback_forward.h"
 #include "base/macros.h"
 
 namespace webrtc {
 class DesktopFrame;
 class DesktopSize;
 }  // namespace webrtc
 
 namespace remoting {
 namespace protocol {
 
 class FrameConsumer {
  public:
+  virtual ~FrameConsumer() {}
+
   // List of supported pixel formats needed by various platforms.
   enum PixelFormat {
     FORMAT_BGRA,  // Used by the Pepper plugin.
     FORMAT_RGBA,  // Used for Android's Bitmap class.
   };
 
   virtual std::unique_ptr<webrtc::DesktopFrame> AllocateFrame(
       const webrtc::DesktopSize& size) = 0;
 
   virtual void DrawFrame(std::unique_ptr<webrtc::DesktopFrame> frame,
                          const base::Closure& done) = 0;
 
   // Returns the preferred pixel encoding for the platform.
   virtual PixelFormat GetPixelFormat() = 0;
 
  protected:
   FrameConsumer() {}
-  virtual ~FrameConsumer() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FrameConsumer);
 };
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_FRAME_CONSUMER_H_