Introduce an IsMutable method on VideoFrameBuffer.

webrtc/common_video/include/video_frame_buffer.h

 /*
  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 15 matching lines @@
   kYPlane = 0,
   kUPlane = 1,
   kVPlane = 2,
   kNumOfPlanes = 3,
 };
 
 // Interface of a simple frame buffer containing pixel data. This interface does
 // not contain any frame metadata such as rotation, timestamp, pixel_width, etc.
 class VideoFrameBuffer : public rtc::RefCountInterface {
  public:
-  // Returns true if this buffer has a single exclusive owner.
+  // Returns true if the caller is exclusive owner, and allowed to
+  // call MutableData.
+  virtual bool IsMutable() = 0;
+
+  // Underlying refcount access, used to implement IsMutable.
+  // TODO(nisse): Demote to protected, as soon as Chrome is changed to
+  // use IsMutable.
   virtual bool HasOneRef() const = 0;
 
   // The resolution of the frame in pixels. For formats where some planes are
   // subsampled, this is the highest-resolution plane.
   virtual int width() const = 0;
   virtual int height() const = 0;
 
   // Returns pointer to the pixel data for a given plane. The memory is owned by
   // the VideoFrameBuffer object and must not be freed by the caller.
   virtual const uint8_t* data(PlaneType type) const = 0;
@@ skipping 22 matching lines @@
  public:
   I420Buffer(int width, int height);
   I420Buffer(int width, int height, int stride_y, int stride_u, int stride_v);
   void InitializeData();
 
   int width() const override;
   int height() const override;
   const uint8_t* data(PlaneType type) const override;
   // Non-const data access is only allowed if HasOneRef() is true to protect
   // against unexpected overwrites.
+  bool IsMutable() override;
   uint8_t* MutableData(PlaneType type) override;
   int stride(PlaneType type) const override;
   void* native_handle() const override;
   rtc::scoped_refptr<VideoFrameBuffer> NativeToI420Buffer() override;
 
   // Create a new buffer and copy the pixel data.
   static rtc::scoped_refptr<I420Buffer> Copy(
       const rtc::scoped_refptr<VideoFrameBuffer>& buffer);
 
  protected:
@@ skipping 14 matching lines @@
 // as their own destructors or conversion methods back to software I420).
 class NativeHandleBuffer : public VideoFrameBuffer {
  public:
   NativeHandleBuffer(void* native_handle, int width, int height);
 
   int width() const override;
   int height() const override;
   const uint8_t* data(PlaneType type) const override;
   int stride(PlaneType type) const override;
   void* native_handle() const override;
+  bool IsMutable() override;
 
  protected:
   void* native_handle_;
   const int width_;
   const int height_;
 };
 
 class WrappedI420Buffer : public webrtc::VideoFrameBuffer {
  public:
   WrappedI420Buffer(int width,
                     int height,
                     const uint8_t* y_plane,
                     int y_stride,
                     const uint8_t* u_plane,
                     int u_stride,
                     const uint8_t* v_plane,
                     int v_stride,
                     const rtc::Callback0<void>& no_longer_used);
   int width() const override;
   int height() const override;
 
+  bool IsMutable() override;
+
   const uint8_t* data(PlaneType type) const override;
 
   int stride(PlaneType type) const override;
   void* native_handle() const override;
 
   rtc::scoped_refptr<VideoFrameBuffer> NativeToI420Buffer() override;
 
  private:
   friend class rtc::RefCountedObject<WrappedI420Buffer>;
   ~WrappedI420Buffer() override;
@@ skipping 12 matching lines @@
 // Helper function to crop |buffer| without making a deep copy. May only be used
 // for non-native frames.
 rtc::scoped_refptr<VideoFrameBuffer> ShallowCenterCrop(
     const rtc::scoped_refptr<VideoFrameBuffer>& buffer,
     int cropped_width,
     int cropped_height);
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_COMMON_VIDEO_INCLUDE_VIDEO_FRAME_BUFFER_H_