Replace const -> constexpr for rtcp Packet Type

webrtc/modules/rtp_rtcp/source/rtcp_packet/bye.cc

Index: webrtc/modules/rtp_rtcp/source/rtcp_packet/bye.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_packet/bye.cc b/webrtc/modules/rtp_rtcp/source/rtcp_packet/bye.cc
index 7b688ab9a4e7cdd04c7c9084c5c8e9ba3dab594c..693b2fc65da3a20286843f619bb689c3876a4be2 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_packet/bye.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_packet/bye.cc
@@ -17,7 +17,7 @@
 
 namespace webrtc {
 namespace rtcp {
-
+constexpr uint8_t Bye::kPacketType;
 // Bye packet (BYE) (RFC 3550).
 //
 //        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
@@ -33,7 +33,7 @@ namespace rtcp {
 Bye::Bye() : sender_ssrc_(0) {}
 
 bool Bye::Parse(const CommonHeader& packet) {
-  RTC_DCHECK(packet.type() == kPacketType);
+  RTC_DCHECK_EQ(packet.type(), kPacketType);
 
   const uint8_t src_count = packet.count();
   // Validate packet.