Let NetEq use the PLC output from a decoder

This change enables NetEq to use the packet concealment audio (aka
PLC) produced by a decoder. The change also includes a new API to the
AudioDecoder interface, which lets the decoder implementation generate
and deliver concealment audio.

Bug: webrtc:9180
Change-Id: Icaacebccf645d4694b0d2d6310f6f2c7132881c4
Reviewed-on: https://webrtc-review.googlesource.com/96340
Commit-Queue: Henrik Lundin <henrik.lundin@webrtc.org>
Reviewed-by: Minyue Li <minyue@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24738}
diff --git a/modules/audio_coding/BUILD.gn b/modules/audio_coding/BUILD.gn
index ff5ae13..a3ff4d4 100644
--- a/modules/audio_coding/BUILD.gn
+++ b/modules/audio_coding/BUILD.gn
@@ -1046,6 +1046,7 @@
     ":neteq_decoder_enum",
     "..:module_api",
     "../..:webrtc_common",
+    "../../api:array_view",
     "../../api:libjingle_peerconnection_api",
     "../../api/audio:audio_frame_api",
     "../../api/audio_codecs:audio_codecs_api",
@@ -2044,6 +2045,7 @@
       "neteq/mock/mock_red_payload_splitter.h",
       "neteq/mock/mock_statistics_calculator.h",
       "neteq/nack_tracker_unittest.cc",
+      "neteq/neteq_decoder_plc_unittest.cc",
       "neteq/neteq_external_decoder_unittest.cc",
       "neteq/neteq_impl_unittest.cc",
       "neteq/neteq_network_stats_unittest.cc",