VideoCaptureDevice: refactor Client::Buffer into an interface

media/video/capture/video_capture_device.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.
 //
 // VideoCaptureDevice is the abstract base class for realizing video capture
 // device support in Chromium. It provides the interface for OS dependent
 // implementations.
 // The class is created and functions are invoked on a thread owned by
 // VideoCaptureManager. Capturing is done on other threads, depending on the OS
 // specific implementation.
@@ skipping 157 matching lines @@
 
    // Interface defining the methods that clients of VideoCapture must have. It
    // is actually two-in-one: clients may implement OnIncomingCapturedData() or
    // ReserveOutputBuffer() + OnIncomingCapturedVideoFrame(), or all of them.
    // All clients must implement OnError().
    class MEDIA_EXPORT Client {
    public:
     // Memory buffer returned by Client::ReserveOutputBuffer().
     class Buffer : public base::RefCountedThreadSafe<Buffer> {
      public:
-      int id() const { return id_; }
-      void* data() const { return data_; }
-      size_t size() const { return size_; }
+      virtual int id() const = 0;
+      virtual void* data() const = 0;
+      virtual size_t size() const = 0;
 
      protected:
       friend class base::RefCountedThreadSafe<Buffer>;
-
-      Buffer(int id, void* data, size_t size)
-          : id_(id), data_(data), size_(size) {}
       virtual ~Buffer() {}
-
-      const int id_;
-      void* const data_;
-      const size_t size_;
     };
 
     virtual ~Client() {}
 
     // Captured a new video frame, data for which is pointed to by |data|.
     //
     // The format of the frame is described by |frame_format|, and is assumed to
     // be tightly packed. This method will try to reserve an output buffer and
     // copy from |data| into the output buffer. If no output buffer is
     // available, the frame will be silently dropped.
@@ skipping 123 matching lines @@
   virtual void CaptureImage() {}
 
  protected:
   static const int kPowerLine50Hz = 50;
   static const int kPowerLine60Hz = 60;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_