Add a flag to actively reset the SRTP parameters

Add a new flag to RtcConfiguration. By setting that flag to true, the
SRTP parameters will be reset whenever the DTLS transports are reset
after every offer/answer negotiation.

The flag is added to Android and Objc wrapper as well.

This should only be used as a workaround for the linked bug, if the
application knows that the other party is affected (for instance,
using a version number).

TBR=sakal@webrtc.org, denicija@webrtc.org

Bug: chromium:835958
Change-Id: I6db025e1c69bf83e1b1908f7df4627430db9920c
Reviewed-on: https://webrtc-review.googlesource.com/83101
Commit-Queue: Zhi Huang <zhihuang@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23587}

sdk/android/api/org/webrtc/PeerConnection.java

@@ -457,6 +457,10 @@ public class PeerConnection {
     // This is an optional wrapper for the C++ webrtc::TurnCustomizer.
     @Nullable public TurnCustomizer turnCustomizer;
 
+    // Actively reset the SRTP parameters whenever the DTLS transports underneath are reset for
+    // every offer/answer negotiation.This is only intended to be a workaround for crbug.com/835958
+    public boolean activeResetSrtpParams;
+
     // TODO(deadbeef): Instead of duplicating the defaults here, we should do
     // something to pick up the defaults from C++. The Objective-C equivalent
     // of RTCConfiguration does that.
@@ -495,6 +499,7 @@ public class PeerConnection {
       enableDtlsSrtp = null;
       networkPreference = AdapterType.UNKNOWN;
       sdpSemantics = SdpSemantics.PLAN_B;
+      activeResetSrtpParams = false;
     }
 
     @CalledByNative("RTCConfiguration")
@@ -682,6 +687,11 @@ public class PeerConnection {
     SdpSemantics getSdpSemantics() {
       return sdpSemantics;
     }
+
+    @CalledByNative("RTCConfiguration")
+    boolean getActiveResetSrtpParams() {
+      return activeResetSrtpParams;
+    }
   };
 
   private final List<MediaStream> localStreams = new ArrayList<>();