Some fixups for AudioController and unit tests

media/audio/linux/audio_manager_linux.cc

Index: media/audio/linux/audio_manager_linux.cc
diff --git a/media/audio/linux/audio_manager_linux.cc b/media/audio/linux/audio_manager_linux.cc
index b3d21f5956308fba572b51b2f70dafdb720984d5..9fa4799fd72a8cfde34a92f2255f7bfaba42b53d 100644
--- a/media/audio/linux/audio_manager_linux.cc
+++ b/media/audio/linux/audio_manager_linux.cc
@@ -59,6 +59,12 @@ AudioManagerLinux::AudioManagerLinux()
 }
 
 AudioManagerLinux::~AudioManagerLinux() {
+  // Make sure we stop the thread first. If we let the default destructor to
+  // destruct the members, we may destroy audio streams before stopping the
+  // thread, resulting an unexpected behavior.
+  // This way we make sure activities of the audio streams are all stopped
+  // before we destroy them.
+  audio_thread_.Stop();
   active_streams_.clear();
 }