Implement RtpCodecParameters::parameters

This will return all the fmtp parameters for the codecs, except for
DTMF codes that don't fit the key=value pattern.

Bug: webrtc:7112
Change-Id: I06a203ff64df2c3bc9bc2082cd0f374718b23510
Reviewed-on: https://webrtc-review.googlesource.com/71801
Commit-Queue: Florent Castelli <orphis@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23250}
diff --git a/sdk/objc/Framework/Headers/WebRTC/RTCRtpCodecParameters.h b/sdk/objc/Framework/Headers/WebRTC/RTCRtpCodecParameters.h
index c7ca2f5..4ba0364 100644
--- a/sdk/objc/Framework/Headers/WebRTC/RTCRtpCodecParameters.h
+++ b/sdk/objc/Framework/Headers/WebRTC/RTCRtpCodecParameters.h
@@ -63,6 +63,9 @@
  **/
 @property(nonatomic, readonly, nullable) NSNumber *numChannels;
 
+/** The "format specific parameters" field from the "a=fmtp" line in the SDP */
+@property(nonatomic, readonly, nonnull) NSDictionary *parameters;
+
 - (instancetype)init NS_DESIGNATED_INITIALIZER;
 
 @end