assert unreachable code in simulcast config

and IWYU

BUG=webrtc:398218412

Change-Id: I6adba61fe9f14f31035f0ff142b51cd991dff2a1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/379280
Commit-Queue: Erik Språng <sprang@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#44012}
diff --git a/video/config/BUILD.gn b/video/config/BUILD.gn
index 17930de..c6d000c 100644
--- a/video/config/BUILD.gn
+++ b/video/config/BUILD.gn
@@ -23,6 +23,7 @@
     "../../api/units:data_rate",
     "../../api/video:resolution",
     "../../api/video:video_codec_constants",
+    "../../api/video:video_frame",
     "../../api/video_codecs:video_codecs_api",
     "../../call/adaptation:resource_adaptation",
     "../../media:media_constants",
diff --git a/video/config/simulcast.cc b/video/config/simulcast.cc
index 5803f3f..a1000db 100644
--- a/video/config/simulcast.cc
+++ b/video/config/simulcast.cc
@@ -19,16 +19,19 @@
 #include <vector>
 
 #include "absl/strings/match.h"
+#include "api/array_view.h"
 #include "api/field_trials_view.h"
-#include "api/video/video_codec_constants.h"
+#include "api/units/data_rate.h"
+#include "api/video/resolution.h"
+#include "api/video/video_codec_type.h"
 #include "media/base/media_constants.h"
 #include "modules/video_coding/utility/simulcast_rate_allocator.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/experiments/field_trial_parser.h"
 #include "rtc_base/experiments/min_video_bitrate_experiment.h"
-#include "rtc_base/experiments/normalize_simulcast_size_experiment.h"
 #include "rtc_base/experiments/rate_control_settings.h"
 #include "rtc_base/logging.h"
+#include "video/config/video_encoder_config.h"
 
 namespace webrtc {
 
@@ -197,6 +200,8 @@
     case webrtc::kVideoCodecH265:
       return 1;
   }
+  RTC_DCHECK_NOTREACHED() << "Unsupported codec.";
+  return 1;
 }
 
 std::vector<SimulcastFormat> GetSimulcastFormats(