Add FrameEncryptor/FrameDecryptor support to Objective C API for WebRTC.

This change adds bindings so that native FrameEncryptor and native FrameDecryptor
objects can be set on the objective C RTCRtpSender and RTCRtpReceiver objects.

Bug: webrtc:9681
Change-Id: Iec4006ea020d6ab6adcc0ad068dcd8fb2738063d
Reviewed-on: https://webrtc-review.googlesource.com/c/103020
Commit-Queue: Benjamin Wright <benwright@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24936}
diff --git a/sdk/BUILD.gn b/sdk/BUILD.gn
index 3d624c7..9e5f4a4 100644
--- a/sdk/BUILD.gn
+++ b/sdk/BUILD.gn
@@ -859,9 +859,11 @@
         "objc/api/peerconnection/RTCRtpParameters+Private.h",
         "objc/api/peerconnection/RTCRtpParameters.h",
         "objc/api/peerconnection/RTCRtpParameters.mm",
+        "objc/api/peerconnection/RTCRtpReceiver+Native.h",
         "objc/api/peerconnection/RTCRtpReceiver+Private.h",
         "objc/api/peerconnection/RTCRtpReceiver.h",
         "objc/api/peerconnection/RTCRtpReceiver.mm",
+        "objc/api/peerconnection/RTCRtpSender+Native.h",
         "objc/api/peerconnection/RTCRtpSender+Private.h",
         "objc/api/peerconnection/RTCRtpSender.h",
         "objc/api/peerconnection/RTCRtpSender.mm",