Delete struct rtc::PacketTime.

Replaced by a int64_t representing time in us. To aid transition of
downstream code, rtc::PacketTime is made an alias for int64_t.

Bug: webrtc:9584
Change-Id: Ic3a5ee87d6de2aad7712894906dab074f1443df9
Reviewed-on: https://webrtc-review.googlesource.com/c/91860
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25503}
diff --git a/media/base/mediachannel.h b/media/base/mediachannel.h
index fefb993..69c7b00 100644
--- a/media/base/mediachannel.h
+++ b/media/base/mediachannel.h
@@ -194,10 +194,10 @@
                             webrtc::MediaTransportInterface* media_transport);
   // Called when a RTP packet is received.
   virtual void OnPacketReceived(rtc::CopyOnWriteBuffer* packet,
-                                const rtc::PacketTime& packet_time) = 0;
+                                int64_t packet_time_us) = 0;
   // Called when a RTCP packet is received.
   virtual void OnRtcpReceived(rtc::CopyOnWriteBuffer* packet,
-                              const rtc::PacketTime& packet_time) = 0;
+                              int64_t packet_time_us) = 0;
   // Called when the socket's ability to send has changed.
   virtual void OnReadyToSend(bool ready) = 0;
   // Called when the network route used for sending packets changed.