Add support for audio input mute detection on all platforms

media/audio/pulse/pulse_input.cc

Index: media/audio/pulse/pulse_input.cc
diff --git a/media/audio/pulse/pulse_input.cc b/media/audio/pulse/pulse_input.cc
index 14ef242759a68d48db6da943ebb899b1089c3cf6..4ae006b210b324eab063ec98475f4e0a89d4cc87 100644
--- a/media/audio/pulse/pulse_input.cc
+++ b/media/audio/pulse/pulse_input.cc
@@ -30,6 +30,7 @@ PulseAudioInputStream::PulseAudioInputStream(AudioManagerPulse* audio_manager,
       channels_(0),
       volume_(0.0),
       stream_started_(false),
+      muted_(false),
       fifo_(params.channels(),
             params.frames_per_buffer(),
             kNumberOfBlocksBufferInFifo),
@@ -199,6 +200,20 @@ double PulseAudioInputStream::GetVolume() {
   }
 }
 
+bool PulseAudioInputStream::IsMuted() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  AutoPulseLock auto_lock(pa_mainloop_);

[no longer working on chromium, 2014/10/14 11:45:42]

please extract these lines of code into a helper method which takes a callback
as input, so GetVolume and IsMuted() will call the same method.

[henrika (OOO until Aug 14), 2014/10/14 14:21:13]

Done.

+  if (!handle_)
+    return false;
+
+  size_t index = pa_stream_get_device_index(handle_);
+  pa_operation* operation = pa_context_get_source_info_by_index(
+      pa_context_, index, &MuteCallback, this);
+  WaitForOperationCompletion(pa_mainloop_, operation);
+
+  return muted_;
+}
+
 // static, used by pa_stream_set_read_callback.
 void PulseAudioInputStream::ReadCallback(pa_stream* handle,
                                          size_t length,
@@ -236,6 +251,21 @@ void PulseAudioInputStream::VolumeCallback(pa_context* context,
   stream->volume_ = static_cast<double>(volume);
 }
 
+// static, used by pa_context_get_source_info_by_index.
+void PulseAudioInputStream::MuteCallback(pa_context* context,
+                                         const pa_source_info* info,
+                                         int error, void* user_data) {
+  PulseAudioInputStream* stream =
+      reinterpret_cast<PulseAudioInputStream*>(user_data);
+
+  if (error) {
+    pa_threaded_mainloop_signal(stream->pa_mainloop_, 0);
+    return;
+  }
+
+  stream->muted_ = static_cast<bool>(info->mute);
+}
+
 // static, used by pa_stream_set_state_callback.
 void PulseAudioInputStream::StreamNotifyCallback(pa_stream* s,
                                                  void* user_data) {