Adding GetInDtx to WebRTC Opus Interface.

Bug: webrtc:11085
Change-Id: Ie9152cbe3f3c70f6febafb877852d68a831bcae9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/159708
Commit-Queue: Minyue Li <minyue@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29834}
diff --git a/modules/audio_coding/codecs/opus/opus_interface.cc b/modules/audio_coding/codecs/opus/opus_interface.cc
index 2f475cb..f98afd7 100644
--- a/modules/audio_coding/codecs/opus/opus_interface.cc
+++ b/modules/audio_coding/codecs/opus/opus_interface.cc
@@ -370,6 +370,18 @@
   }
 }
 
+int32_t WebRtcOpus_GetInDtx(OpusEncInst* inst) {
+  if (!inst) {
+    return -1;
+  }
+  int32_t in_dtx;
+  if (ENCODER_CTL(inst, OPUS_GET_IN_DTX(&in_dtx)) == 0) {
+    return in_dtx;
+  } else {
+    return -1;
+  }
+}
+
 int16_t WebRtcOpus_DecoderCreate(OpusDecInst** inst,
                                  size_t channels,
                                  int sample_rate_hz) {