Add min_bitrate_bps to RTCRtpEncodingParameters.

This is an ObjC followup to https://webrtc-review.googlesource.com/c/src/+/78741.

This CL only adds the field to the API, but does not wire it up.

Bug: webrtc:9341
Change-Id: Id6b1ac681324120bc90158029da7a80bf99aa512
Reviewed-on: https://webrtc-review.googlesource.com/81182
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Commit-Queue: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23524}
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCRtpEncodingParameters.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCRtpEncodingParameters.mm
index 8e72d18..8521862 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCRtpEncodingParameters.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCRtpEncodingParameters.mm
@@ -14,6 +14,7 @@
 
 @synthesize isActive = _isActive;
 @synthesize maxBitrateBps = _maxBitrateBps;
+@synthesize minBitrateBps = _minBitrateBps;
 @synthesize ssrc = _ssrc;
 
 - (instancetype)init {
@@ -28,6 +29,10 @@
       _maxBitrateBps =
           [NSNumber numberWithInt:*nativeParameters.max_bitrate_bps];
     }
+    if (nativeParameters.min_bitrate_bps) {
+      _minBitrateBps =
+          [NSNumber numberWithInt:*nativeParameters.min_bitrate_bps];
+    }
     if (nativeParameters.ssrc) {
       _ssrc = [NSNumber numberWithUnsignedLong:*nativeParameters.ssrc];
     }
@@ -41,6 +46,9 @@
   if (_maxBitrateBps != nil) {
     parameters.max_bitrate_bps = rtc::Optional<int>(_maxBitrateBps.intValue);
   }
+  if (_minBitrateBps != nil) {
+    parameters.min_bitrate_bps = rtc::Optional<int>(_minBitrateBps.intValue);
+  }
   if (_ssrc != nil) {
     parameters.ssrc = rtc::Optional<uint32_t>(_ssrc.unsignedLongValue);
   }