Add latency to remote source api.

Latency corresponds to base minimum delay on NetEq.

Bug: webrtc:10287
Change-Id: I538d202e3e4fe07b779c46bf560e2fde38e0468e
Reviewed-on: https://webrtc-review.googlesource.com/c/121704
Commit-Queue: Ruslan Burakov <kuddai@google.com>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26724}
diff --git a/api/media_stream_interface.cc b/api/media_stream_interface.cc
index 73566c4..b55a840 100644
--- a/api/media_stream_interface.cc
+++ b/api/media_stream_interface.cc
@@ -32,4 +32,8 @@
   return {};
 }
 
+double AudioSourceInterface::GetLatency() const {
+  return 0.0;
+}
+
 }  // namespace webrtc