Clean away unused enum RtpPacketSendResult

Also updates outdated comment.

Bug: webrtc:8052
Change-Id: Ib88c2894bdda5efcf36d8d7dfbacbe96edf1b549
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/152180
Commit-Queue: Erik Språng <sprang@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29168}

modules/rtp_rtcp/include/rtp_rtcp_defines.h

@@ -492,13 +492,5 @@ class SendPacketObserver {
                             int64_t capture_time_ms,
                             uint32_t ssrc) = 0;
 };
-
-// Status returned from TimeToSendPacket() family of callbacks.
-enum class RtpPacketSendResult {
-  kSuccess,               // Packet sent OK.
-  kTransportUnavailable,  // Network unavailable, try again later.
-  kPacketNotFound  // SSRC/sequence number does not map to an available packet.
-};
-
 }  // namespace webrtc
 #endif  // MODULES_RTP_RTCP_INCLUDE_RTP_RTCP_DEFINES_H_

modules/rtp_rtcp/source/rtp_sender.h

@@ -89,8 +89,9 @@ class RTPSender {
   bool IsRtpHeaderExtensionRegistered(RTPExtensionType type) const;
   int32_t DeregisterRtpHeaderExtension(RTPExtensionType type);
 
-  // Returns an RtpPacketSendResult indicating success, network unavailable,
-  // or packet not found.
+  // Tries to send packet to transport. Also updates any timing extensions,
+  // calls observers waiting for packet send events, and updates stats.
+  // Returns true if packet belongs to this RTP module, false otherwise.
   bool TrySendPacket(RtpPacketToSend* packet,
                      const PacedPacketInfo& pacing_info);
   bool SupportsPadding() const;