Moved FrameKey to api/video/encoded_frame.h and renamed it to VideoLayerFrameId.

Since we want the VideoStreamDecoder to callback with the last
continuous frame we need to move the FrameKey into the public API.

Bug: webrtc:8909
Change-Id: I39634145d848b8163778e31a1e0d04d91f9bbeb8
Reviewed-on: https://webrtc-review.googlesource.com/60864
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22495}
diff --git a/modules/video_coding/frame_buffer2.h b/modules/video_coding/frame_buffer2.h
index df8d8fe..c05fb8a 100644
--- a/modules/video_coding/frame_buffer2.h
+++ b/modules/video_coding/frame_buffer2.h
@@ -78,23 +78,6 @@
   void UpdateRtt(int64_t rtt_ms);
 
  private:
-  struct FrameKey {
-    FrameKey() : picture_id(-1), spatial_layer(0) {}
-    FrameKey(int64_t picture_id, uint8_t spatial_layer)
-        : picture_id(picture_id), spatial_layer(spatial_layer) {}
-
-    bool operator<(const FrameKey& rhs) const {
-      if (picture_id == rhs.picture_id)
-        return spatial_layer < rhs.spatial_layer;
-      return picture_id < rhs.picture_id;
-    }
-
-    bool operator<=(const FrameKey& rhs) const { return !(rhs < *this); }
-
-    int64_t picture_id;
-    uint8_t spatial_layer;
-  };
-
   struct FrameInfo {
     // The maximum number of frames that can depend on this frame.
     static constexpr size_t kMaxNumDependentFrames = 8;
@@ -103,7 +86,7 @@
     // on this frame.
     // TODO(philipel): Add simple modify/access functions to prevent adding too
     // many |dependent_frames|.
-    FrameKey dependent_frames[kMaxNumDependentFrames];
+    VideoLayerFrameId dependent_frames[kMaxNumDependentFrames];
     size_t num_dependent_frames = 0;
 
     // A frame is continiuous if it has all its referenced/indirectly
@@ -124,7 +107,7 @@
     std::unique_ptr<EncodedFrame> frame;
   };
 
-  using FrameMap = std::map<FrameKey, FrameInfo>;
+  using FrameMap = std::map<VideoLayerFrameId, FrameInfo>;
 
   // Check that the references of |frame| are valid.
   bool ValidReferences(const EncodedFrame& frame) const;