Avoid reporting 0 as input level when AudioProcessing zero out the audio data

content/renderer/media/media_stream_audio_level_calculator.cc

 // Copyright 2014 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 "content/renderer/media/media_stream_audio_level_calculator.h"
 
 #include "base/logging.h"
 #include "base/stl_util.h"
 
 namespace content {
@@ skipping 22 matching lines @@
     : counter_(0),
       max_amplitude_(0),
       level_(0) {
 }
 
 MediaStreamAudioLevelCalculator::~MediaStreamAudioLevelCalculator() {
 }
 
 int MediaStreamAudioLevelCalculator::Calculate(const int16* audio_data,
                                                int number_of_channels,
-                                               int number_of_frames) {
+                                               int number_of_frames,
+                                               bool has_energy) {
   DCHECK(thread_checker_.CalledOnValidThread());
   // |level_| is updated every 10 callbacks. For the case where callback comes
   // every 10ms, |level_| will be updated approximately every 100ms.
   static const int kUpdateFrequency = 10;
 
   int max = MaxAmplitude(audio_data, number_of_channels * number_of_frames);
   max_amplitude_ = std::max(max_amplitude_, max);
 
   if (counter_++ == kUpdateFrequency) {
-    level_ = max_amplitude_;
+    level_ = (max_amplitude_ == 0 ? has_energy : max_amplitude_);
 
     // Decay the absolute maximum amplitude by 1/4.
     max_amplitude_ >>= 2;
 
     // Reset the counter.
     counter_ = 0;
   }
 
   return level_;
 }
 
 }  // namespace content