Revert "Implement H264 simulcast support and generalize SimulcastEncoderAdapter use for H264 & VP8."

This reverts commit 07efe436c9002e139845f62486e3ee4e29f0d85b.

Reason for revert: Breaks downstream project.

cricket::GetSimulcastConfig method signature has been updated.
I think you can get away with a default value for temporal_layers_supported (and then you can remove it after a few days when projects will be updated).


Original change's description:
> Implement H264 simulcast support and generalize SimulcastEncoderAdapter use for H264 & VP8.
> 
> * Move SimulcastEncoderAdapter out under modules/video_coding
> * Move SimulcastRateAllocator back out to modules/video_coding/utility
> * Move TemporalLayers and ScreenshareLayers to modules/video_coding/utility
> * Move any VP8 specific code - such as temporal layer bitrate budgeting -
>   under codec type dependent conditionals.
> * Plumb the simulcast index for H264 in the codec specific and RTP format data structures.
> 
> Bug: webrtc:5840
> Change-Id: Ieced8a00e38f273c1a6cfd0f5431a87d07b8f44e
> Reviewed-on: https://webrtc-review.googlesource.com/64100
> Commit-Queue: Harald Alvestrand <hta@webrtc.org>
> Reviewed-by: Stefan Holmer <stefan@webrtc.org>
> Reviewed-by: Erik Språng <sprang@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#23705}

TBR=sprang@webrtc.org,stefan@webrtc.org,mflodman@webrtc.org,hta@webrtc.org,sergio.garcia.murillo@gmail.com,titovartem@webrtc.org,agouaillard@gmail.com

Change-Id: Ic9d3b1eeaf195bb5ec2063954421f5e77866d663
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:5840
Reviewed-on: https://webrtc-review.googlesource.com/84760
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23710}
diff --git a/modules/video_coding/video_codec_initializer.cc b/modules/video_coding/video_codec_initializer.cc
index 04554c1..7ef6cfe 100644
--- a/modules/video_coding/video_codec_initializer.cc
+++ b/modules/video_coding/video_codec_initializer.cc
@@ -13,13 +13,14 @@
 #include "api/video_codecs/video_encoder.h"
 #include "common_types.h"  // NOLINT(build/include)
 #include "common_video/include/video_bitrate_allocator.h"
+#include "modules/video_coding/codecs/vp8/screenshare_layers.h"
+#include "modules/video_coding/codecs/vp8/simulcast_rate_allocator.h"
+#include "modules/video_coding/codecs/vp8/temporal_layers.h"
 #include "modules/video_coding/codecs/vp9/svc_config.h"
 #include "modules/video_coding/codecs/vp9/svc_rate_allocator.h"
 #include "modules/video_coding/include/video_coding_defines.h"
 #include "modules/video_coding/utility/default_video_bitrate_allocator.h"
-#include "modules/video_coding/utility/simulcast_rate_allocator.h"
 #include "rtc_base/logging.h"
-#include "rtc_base/system/fallthrough.h"
 #include "system_wrappers/include/clock.h"
 
 namespace webrtc {
@@ -52,8 +53,7 @@
 
   switch (codec.codecType) {
     case kVideoCodecVP8:
-      RTC_FALLTHROUGH();
-    case kVideoCodecH264:
+      // Set up default VP8 temporal layer factory, if not provided.
       rate_allocator.reset(new SimulcastRateAllocator(codec));
       break;
     case kVideoCodecVP9: