Add support for audio input mute detection on all platforms

media/audio/win/audio_low_latency_input_win.cc

Index: media/audio/win/audio_low_latency_input_win.cc
diff --git a/media/audio/win/audio_low_latency_input_win.cc b/media/audio/win/audio_low_latency_input_win.cc
index 9fe061b7682b6e7ceeb3f256307a8c34293d8b2d..2a6f4a6c31a869f02e5fbed7d8f0d996bb3ff0d3 100644
--- a/media/audio/win/audio_low_latency_input_win.cc
+++ b/media/audio/win/audio_low_latency_input_win.cc
@@ -253,7 +253,7 @@ void WASAPIAudioInputStream::SetVolume(double volume) {
 }
 
 double WASAPIAudioInputStream::GetVolume() {
-  DLOG_IF(ERROR, !opened_) << "Open() has not been called successfully";
+  DCHECK(opened_) << "Open() has not been called successfully";
   if (!opened_)
     return 0.0;
 
@@ -265,6 +265,20 @@ double WASAPIAudioInputStream::GetVolume() {
   return static_cast<double>(level);
 }
 
+bool WASAPIAudioInputStream::IsMuted() {
+  DCHECK(opened_) << "Open() has not been called successfully";
+  DCHECK(CalledOnValidThread());
+  if (!opened_)
+    return false;
+
+  // Retrieves the current muting state for the audio session.
+  BOOL is_muted = FALSE;
+  HRESULT hr = simple_audio_volume_->GetMute(&is_muted);
+  DLOG_IF(WARNING, FAILED(hr)) << "Failed to get input master volume.";
+
+  return (is_muted == TRUE) ? true : false;

[tommi (sloooow) - chröme, 2014/10/10 15:54:36]

checking for TRUE always makes me nervous on windows. Who knows what the
implementation might do :)  S_FALSE is 1, TRUE is 1... are you relying on a
bitwise operator!() (i.e. complement) - if so then !FALSE is not equal to
TRUE... VARIANT_TRUE is furthermore defined as -1, which actually is a
complement of 0 (although VARIANT_BOOL is 16 bit... sigh)...  Anyway, it's a
mess. (also see
http://blogs.msdn.com/b/oldnewthing/archive/2004/12/22/329884.aspx)

So, for my piece of mind, please just do:

return is_muted != FALSE;

[henrika (OOO until Aug 14), 2014/10/13 12:27:17]

Thx. Actually checked the exact same link before making my first patch. Using
your style now.

+}
+
 // static
 AudioParameters WASAPIAudioInputStream::GetInputStreamParameters(
     const std::string& device_id) {