Move definition of SpatialLayer to api/video_codecs/spatial_layer.h

Bug: webrtc:7660
Change-Id: I54009ebc5f65b6875a8c079ab5264e0c5ce9f654
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/181500
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31942}
diff --git a/modules/video_coding/video_codec_initializer.cc b/modules/video_coding/video_codec_initializer.cc
index 2859dd0..777056f 100644
--- a/modules/video_coding/video_codec_initializer.cc
+++ b/modules/video_coding/video_codec_initializer.cc
@@ -95,7 +95,7 @@
   int max_framerate = 0;
 
   for (size_t i = 0; i < streams.size(); ++i) {
-    SimulcastStream* sim_stream = &video_codec.simulcastStream[i];
+    SpatialLayer* sim_stream = &video_codec.simulcastStream[i];
     RTC_DCHECK_GT(streams[i].width, 0);
     RTC_DCHECK_GT(streams[i].height, 0);
     RTC_DCHECK_GT(streams[i].max_framerate, 0);