[Chromecast] Fade in after a mixer input stream has skipped

chromecast/media/cma/backend/alsa/stream_mixer_alsa.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chromecast/media/cma/backend/alsa/stream_mixer_alsa.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 #include <utility>
@@ skipping 767 matching lines @@
         LOG(ERROR) << "Failed to get status";
         return false;
       }
 
       int frames_in_buffer =
           alsa_buffer_size_ - alsa_->PcmStatusGetAvail(pcm_status_);
       if (alsa_->PcmStatusGetState(pcm_status_) == SND_PCM_STATE_XRUN ||
           frames_in_buffer < min_frames_in_buffer) {
         // If there has been (or soon will be) an underrun, continue without the
         // empty primary input stream.
+        input->OnSkipped();
         continue;
       }
 
       // A primary input cannot provide any data, so wait until later.
       retry_write_frames_timer_->Start(
           FROM_HERE, base::TimeDelta::FromMilliseconds(kMinBufferedDataMs / 2),
           base::Bind(&StreamMixerAlsa::WriteFrames, base::Unretained(this)));
       return false;
+    } else {
+      input->OnSkipped();
     }
   }
 
   if (active_inputs.empty()) {
-    // No inputs have any data to provide.
-    if (!inputs_.empty()) {
-      return false;  // If there are some inputs, don't fill with silence.
-    }
-
-    // If we have no inputs, fill with silence to avoid underrun.
+    // No inputs have any data to provide. Fill with silence to avoid underrun.
     chunk_size = kPreventUnderrunChunkSize;
     if (!mixed_ || mixed_->frames() < chunk_size) {
       mixed_ = ::media::AudioBus::Create(kNumOutputChannels, chunk_size);
     }
 
     mixed_->Zero();
     WriteMixedPcm(*mixed_, chunk_size, true /* is_silence */);
     return true;
   }
 
@@ skipping 126 matching lines @@
   DCHECK(std::find(loopback_observers_.begin(), loopback_observers_.end(),
                    observer) != loopback_observers_.end());
   loopback_observers_.erase(std::remove(loopback_observers_.begin(),
                                         loopback_observers_.end(), observer),
                             loopback_observers_.end());
   observer->OnRemoved();
 }
 
 }  // namespace media
 }  // namespace chromecast