New enum ScalabilityMode.

Used instead of string representation in lower-levels of encoder configuration, to avoid string comparisons (with risk of misspelling) in lots of places.

Bug: webrtc:11607
Change-Id: I4d51c2265aac297c29976d2aa601d8ffb33b7326
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/259870
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36706}
diff --git a/modules/video_coding/video_codec_initializer_unittest.cc b/modules/video_coding/video_codec_initializer_unittest.cc
index 902f991..85efa46 100644
--- a/modules/video_coding/video_codec_initializer_unittest.cc
+++ b/modules/video_coding/video_codec_initializer_unittest.cc
@@ -430,7 +430,7 @@
   VideoEncoderConfig config;
   config.codec_type = VideoCodecType::kVideoCodecAV1;
   std::vector<VideoStream> streams = {DefaultStream()};
-  streams[0].scalability_mode = "L1T2";
+  streams[0].scalability_mode = ScalabilityMode::kL1T2;
 
   VideoCodec codec;
   EXPECT_TRUE(VideoCodecInitializer::SetupCodec(config, streams, &codec));
@@ -445,7 +445,7 @@
   VideoEncoderConfig config;
   config.codec_type = VideoCodecType::kVideoCodecAV1;
   std::vector<VideoStream> streams = {DefaultStream()};
-  streams[0].scalability_mode = "L2T2";
+  streams[0].scalability_mode = ScalabilityMode::kL2T2;
 
   VideoCodec codec;
   EXPECT_TRUE(VideoCodecInitializer::SetupCodec(config, streams, &codec));
@@ -465,7 +465,7 @@
   VideoEncoderConfig config;
   config.codec_type = VideoCodecType::kVideoCodecAV1;
   std::vector<VideoStream> streams = {DefaultStream()};
-  streams[0].scalability_mode = "L2T2";
+  streams[0].scalability_mode = ScalabilityMode::kL2T2;
   config.spatial_layers = {};
 
   VideoCodec codec;
@@ -479,7 +479,7 @@
   VideoEncoderConfig config;
   config.codec_type = VideoCodecType::kVideoCodecAV1;
   std::vector<VideoStream> streams = {DefaultStream()};
-  streams[0].scalability_mode = "L2T2";
+  streams[0].scalability_mode = ScalabilityMode::kL2T2;
   config.spatial_layers.resize(2);
   config.spatial_layers[0].active = true;
   config.spatial_layers[1].active = false;