Make TransformableVideoFrameInterface::GetMetadata pure virtual.

GetMetadata() has been implemented downstream and can be made pure
virtual.

Bug: chromium:1069295
Change-Id: I62a3be6106552d2d82d8c413c6f523d31626b0d8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/175001
Commit-Queue: Marina Ciocea <marinaciocea@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31281}
diff --git a/api/frame_transformer_interface.h b/api/frame_transformer_interface.h
index 753c7f4..2cfe6ed 100644
--- a/api/frame_transformer_interface.h
+++ b/api/frame_transformer_interface.h
@@ -50,14 +50,7 @@
   // webrtc::RtpDescriptorAuthentication is exposed in api/.
   virtual std::vector<uint8_t> GetAdditionalData() const = 0;
 
-  // TODO(bugs.webrtc.org/11380) make pure virtual after implementating it
-  // downstream.
-  virtual const VideoFrameMetadata& GetMetadata() const { return metadata_; }
-
- private:
-  // TODO(bugs.webrtc.org/11380) remove from interface once GetRtpVideoHeader is
-  // pure virtual.
-  VideoFrameMetadata metadata_;
+  virtual const VideoFrameMetadata& GetMetadata() const = 0;
 };
 
 // Extends the TransformableFrameInterface to expose audio-specific information.
diff --git a/api/video/video_frame_metadata.h b/api/video/video_frame_metadata.h
index ce9b2a1..2e93098 100644
--- a/api/video/video_frame_metadata.h
+++ b/api/video/video_frame_metadata.h
@@ -27,7 +27,6 @@
 class VideoFrameMetadata {
  public:
   explicit VideoFrameMetadata(const RTPVideoHeader& header);
-  VideoFrameMetadata() = default;
   VideoFrameMetadata(const VideoFrameMetadata&) = default;
   VideoFrameMetadata& operator=(const VideoFrameMetadata&) = default;