Add mute state field to AudioFrame.

webrtc/modules/audio_mixer/frame_combiner.cc

Index: webrtc/modules/audio_mixer/frame_combiner.cc
diff --git a/webrtc/modules/audio_mixer/frame_combiner.cc b/webrtc/modules/audio_mixer/frame_combiner.cc
index d08ed0f4739ba77b0fe0f5ab4dc4f8cc12fed397..c248d5e89a5a46168e700e04f10e51fdecdfc0b5 100644
--- a/webrtc/modules/audio_mixer/frame_combiner.cc
+++ b/webrtc/modules/audio_mixer/frame_combiner.cc
@@ -35,10 +35,15 @@ void CombineOneFrame(const AudioFrame* input_frame,
                      AudioFrame* audio_frame_for_mixing) {
   audio_frame_for_mixing->timestamp_ = input_frame->timestamp_;
   audio_frame_for_mixing->elapsed_time_ms_ = input_frame->elapsed_time_ms_;
-  std::copy(input_frame->data_,
-            input_frame->data_ +
-                input_frame->num_channels_ * input_frame->samples_per_channel_,
-            audio_frame_for_mixing->data_);
+  if (!input_frame->muted()) {
+    size_t length =
+        input_frame->num_channels_ * input_frame->samples_per_channel_;
+    const int16_t* input_data = input_frame->data();
+    std::copy(input_data, input_data + length,
+              audio_frame_for_mixing->mutable_data());
+  } else {
+    AudioFrameOperations::Mute(audio_frame_for_mixing);
+  }
 }
 
 std::unique_ptr<AudioProcessing> CreateLimiter() {
@@ -105,7 +110,7 @@ void FrameCombiner::Combine(const std::vector<AudioFrame*>& mix_list,
     std::vector<rtc::ArrayView<const int16_t>> input_frames;
     for (size_t i = 0; i < mix_list.size(); ++i) {
       input_frames.push_back(rtc::ArrayView<const int16_t>(
-          mix_list[i]->data_, samples_per_channel * number_of_channels));
+          mix_list[i]->data(), samples_per_channel * number_of_channels));
     }
     CombineMultipleFrames(input_frames, audio_frame_for_mixing);
   }
@@ -133,6 +138,7 @@ void FrameCombiner::CombineMultipleFrames(
   add_buffer.fill(0);
 
   for (const auto& frame : input_frames) {
+    // TODO(yujo): skip this for muted input frames.
     std::transform(frame.begin(), frame.end(), add_buffer.begin(),
                    add_buffer.begin(), std::plus<int32_t>());
   }
@@ -140,7 +146,7 @@ void FrameCombiner::CombineMultipleFrames(
   if (use_apm_limiter_) {
     // Halve all samples to avoid saturation before limiting.
     std::transform(add_buffer.begin(), add_buffer.begin() + frame_length,
-                   audio_frame_for_mixing->data_, [](int32_t a) {
+                   audio_frame_for_mixing->mutable_data(), [](int32_t a) {
                      return rtc::saturated_cast<int16_t>(a / 2);
                    });
 
@@ -165,7 +171,7 @@ void FrameCombiner::CombineMultipleFrames(
     AudioFrameOperations::Add(*audio_frame_for_mixing, audio_frame_for_mixing);
   } else {
     std::transform(add_buffer.begin(), add_buffer.begin() + frame_length,
-                   audio_frame_for_mixing->data_,
+                   audio_frame_for_mixing->mutable_data(),
                    [](int32_t a) { return rtc::saturated_cast<int16_t>(a); });
   }
 }