NetEQ: fix initial decoder frame length.

Bug: webrtc:10548
Change-Id: If020ce0e5bef57f4f783dbc47995fd0c9f7e2137
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/161046
Reviewed-by: Ivo Creusen <ivoc@webrtc.org>
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29960}
diff --git a/modules/audio_coding/neteq/neteq_impl.cc b/modules/audio_coding/neteq/neteq_impl.cc
index feabb37..05e7b73 100644
--- a/modules/audio_coding/neteq/neteq_impl.cc
+++ b/modules/audio_coding/neteq/neteq_impl.cc
@@ -151,7 +151,7 @@
   last_output_sample_rate_hz_ = fs;
   output_size_samples_ = static_cast<size_t>(kOutputSizeMs * 8 * fs_mult_);
   controller_->SetSampleRate(fs_hz_, output_size_samples_);
-  decoder_frame_length_ = 3 * output_size_samples_;
+  decoder_frame_length_ = 2 * output_size_samples_;  // 20 ms.
   if (create_components) {
     SetSampleRateAndChannels(fs, 1);  // Default is 1 channel.
   }