Reduce kMaxSimulcastStreams to 3

Because of webrtc:10801, we don't actually support 4 simulcast layers but 3.
Until this is fixed, we limit the value to what we can currently handle.

Bug: webrtc:8785
Change-Id: I513b7c8d4c889fa0d80c91adc1c4f874acb86fdc
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/144625
Commit-Queue: Florent Castelli <orphis@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28487}
diff --git a/api/video/video_codec_constants.h b/api/video/video_codec_constants.h
index e4e4b0f..6b6feee 100644
--- a/api/video/video_codec_constants.h
+++ b/api/video/video_codec_constants.h
@@ -14,7 +14,7 @@
 namespace webrtc {
 
 enum : int { kMaxEncoderBuffers = 8 };
-enum : int { kMaxSimulcastStreams = 4 };
+enum : int { kMaxSimulcastStreams = 3 };
 enum : int { kMaxSpatialLayers = 5 };
 enum : int { kMaxTemporalStreams = 4 };
 
diff --git a/pc/peer_connection_simulcast_unittest.cc b/pc/peer_connection_simulcast_unittest.cc
index 4b1f09b..cb36bb1 100644
--- a/pc/peer_connection_simulcast_unittest.cc
+++ b/pc/peer_connection_simulcast_unittest.cc
@@ -406,8 +406,8 @@
 TEST_F(PeerConnectionSimulcastTests, RejectedSimulcastLayersAreDeactivated) {
   auto local = CreatePeerConnectionWrapper();
   auto remote = CreatePeerConnectionWrapper();
-  auto layers = CreateLayers({"1", "2", "3", "4"}, true);
-  auto expected_layers = CreateLayers({"2", "3", "4"}, true);
+  auto layers = CreateLayers({"1", "2", "3"}, true);
+  auto expected_layers = CreateLayers({"2", "3"}, true);
   auto transceiver = AddTransceiver(local.get(), layers);
   auto offer = local->CreateOfferAndSetAsLocal();
   {