Add support for audio input mute detection on all platforms

media/audio/alsa/alsa_input.cc

 // Copyright 2013 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 "media/audio/alsa/alsa_input.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 318 matching lines @@
       mixer_element_handle_, static_cast<snd_mixer_selem_channel_id_t>(0),
       &current_volume);
   if (error < 0) {
     DLOG(WARNING) << "Unable to get volume for " << device_name_;
     return 0.0;
   }
 
   return static_cast<double>(current_volume);
 }
 
+bool AlsaPcmInputStream::IsMuted() {
+  return false;
+}
+
 void AlsaPcmInputStream::HandleError(const char* method, int error) {
   LOG(WARNING) << method << ": " << wrapper_->StrError(error);
   callback_->OnError(this);
 }
 
 }  // namespace media