Remove media::VideoDecodeContext as it has no implementation and is unused.

media/video/video_decode_context.h

-// Copyright (c) 2010 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 MEDIA_VIDEO_VIDEO_DECODE_CONTEXT_H_
-#define MEDIA_VIDEO_VIDEO_DECODE_CONTEXT_H_
-
-#include <vector>
-
-#include "base/task.h"
-#include "media/base/video_frame.h"
-
-namespace media {
-
-class VideoFrame;
-
-// A VideoDecodeContext is used by VideoDecodeEngine to provide the following
-// functions:
-//
-// 1. Provides access to hardware video decoding device.
-// 2. Allocate VideoFrame objects that are used to carry the decoded video
-//    frames.
-// 3. Upload a device specific buffer to some common VideoFrame storage types.
-//    In many cases a VideoDecodeEngine provides its own buffer, these buffer
-//    are usually device specific and a conversion step is needed. Instead of
-//    handling these many cases in the renderer a VideoDecodeContext is used
-//    to convert the device specific buffer to a common storage format, e.g.
-//    GL textures or system memory. This way we keep the device specific code
-//    in the VideoDecodeEngine and VideoDecodeContext pair.
-class VideoDecodeContext {
- public:
-  virtual ~VideoDecodeContext() {}
-
-  // Obtain a handle to the hardware video decoder device. The type of the
-  // handle is a contract between the implementation of VideoDecodeContext and
-  // VideoDecodeEngine.
-  //
-  // If a hardware device is not needed this method should return NULL.
-  virtual void* GetDevice() = 0;
-
-  // Allocate |n| video frames with dimension |width| and |height|. |task|
-  // is called when allocation has completed.
-  //
-  // |frames| is the output parameter for VideFrame(s) allocated.
-  virtual void AllocateVideoFrames(
-      int n, size_t width, size_t height, VideoFrame::Format format,
-      std::vector<scoped_refptr<VideoFrame> >* frames,
-      Task* task) = 0;
-
-  // Release all video frames allocated by the context. After making this call
-  // VideoDecodeEngine should not use the VideoFrame allocated because they
-  // could be destroyed.
-  virtual void ReleaseAllVideoFrames() = 0;
-
-  // Upload a device specific buffer to a video frame. The video frame was
-  // allocated via AllocateVideoFrames().
-  // This method is used if a VideoDecodeEngine cannot write directly to a
-  // VideoFrame, e.g. upload should be done on a different thread, the subsystem
-  // require some special treatment to generate a VideoFrame. The goal is to
-  // keep VideoDecodeEngine a reusable component and also adapt to different
-  // system by having a different VideoDecodeContext.
-  //
-  // |frame| is a VideoFrame allocated via AllocateVideoFrames().
-  //
-  // |buffer| is of type void*, it is of an internal type in VideoDecodeEngine
-  // that points to the buffer that contains the video frame.
-  // Implementor should know how to handle it.
-  //
-  // |task| is executed if the operation was completed successfully.
-  virtual void ConvertToVideoFrame(void* buffer,
-                                   scoped_refptr<VideoFrame> frame,
-                                   Task* task) = 0;
-
-  // Destroy this context asynchronously. When the operation is done |task|
-  // is called. It is safe to delete this object only after |task| is called.
-  //
-  // ReleaseVideoFrames() need to be called with all the video frames allocated
-  // before making this call.
-  virtual void Destroy(Task* task) = 0;
-};
-
-}  // namespace media
-
-#endif  // MEDIA_VIDEO_VIDEO_DECODE_CONTEXT_H_