message: Deprecate TransformableVideoFrame GetAdditionalData
  It's unused in Chromium and internally - GetMetadata() provides
  sufficient information.
  Cr-Commit-Position: refs/heads/main@{#39287}
diff: @@ -57,9 +57,9 @@ class TransformableVideoFrameInterface : public TransformableFrameInterface {
  // when the transformation applied to the frame is encryption/decryption, the
  // additional data holds the serialized generic frame descriptor extension
  // calculated in webrtc::RtpDescriptorAuthentication.
  - // TODO(bugs.webrtc.org/11380) remove from interface once
  - // webrtc::RtpDescriptorAuthentication is exposed in api/.
  - virtual std::vector<uint8_t> GetAdditionalData() const = 0;
  + // This has been superseeded by GetMetadata() and will be removed shortly.
  + [[deprecated("https://crbug.com/1414370")]] virtual std::vector<uint8_t>
  + GetAdditionalData() const = 0;
  virtual const VideoFrameMetadata& GetMetadata() const = 0;
  // TODO(https://crbug.com/webrtc/14709): Make pure virtual when Chromium MOCK
  