p2p_transport_channel: Add estimated disconnected time to CandidatePairChangeEvent

This patch adds a computed estimate on how long the ice stack
was disconnected before switching to a new connection.

The metric is currently computed as now - max(connection->last_data_recevied())
and has resonably good precision.

Bug: webrtc:11862
Change-Id: I8950d55f0eadcf164de089cdb715b4f7eed0a4c3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/182002
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31969}

sdk/android/src/jni/pc/peer_connection.cc

@@ -128,7 +128,8 @@ ScopedJavaLocalRef<jobject> NativeToJavaCandidatePairChange(
       env, NativeToJavaCandidate(env, selected_pair.local_candidate()),
       NativeToJavaCandidate(env, selected_pair.remote_candidate()),
       static_cast<int>(event.last_data_received_ms),
-      NativeToJavaString(env, event.reason));
+      NativeToJavaString(env, event.reason),
+      static_cast<int>(event.estimated_disconnected_time_ms));
 }
 
 }  // namespace