Let default device in PulseAudio be the system default device

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 8d4aeea2079d201a69e52fb48e4344680c467d70..6b43e413c1d11d32214387f75109d9abf22858f9 100644
--- a/media/audio/pulse/pulse_input.cc
+++ b/media/audio/pulse/pulse_input.cc
@@ -48,9 +48,36 @@ PulseAudioInputStream::~PulseAudioInputStream() {
   DCHECK(!handle_);
 }
 
+// static, used by pa_context_get_server_info.
+void PulseAudioInputStream::UseSystemDefaultInputDeviceCallback(

[Henrik Grunell, 2016/03/07 11:37:17]

Since this function is only used in this cc file, remove from class and make it
an ordinary function under anonymous namespace. Same for output.

[rchtara, 2016/03/08 17:28:16]

I tried to do that by making it friend with PulseAudioInputStream but
unfortunately it's not possible : the function is declared in the anonymous
namespace of pulse_input.cc, so can't be used from pulse_input.cc,
As the function is in the anonymous NS in the pulse_input.cc, it's not possible
to refer to it in pulse_input.h.
There many ways to solve this issue: we can for example make it a part of media
NS. However this is going to work but make it accessible for anyone, which is
worst than the current situation as it's currently private and accessible from
PulseAudioInputStream.

[Henrik Grunell, 2016/03/09 00:49:16]

I don't understand what the problem is. Is it accessing the member variables?
See next comment.

[rchtara, 2016/03/09 16:16:09]

If we put the function UseSystemDefaultInputDeviceCallback in the anonymous
namespace of pulse_input.cc, it's not visible outside this file. so we cannot
access it from the header file pulse_input.h and so we cannot make it friends
with PulseAudioInputStream.

So, in this case,it's not possible to make them friends.
As solution we can make some setters or getters for anything needed in
UseSystemDefaultInputDeviceCallback or we can make the function private static 
member of PulseAudioInputStream... 

+    pa_context* context,
+    const pa_server_info* info,
+    void* user_data) {
+  PulseAudioInputStream* stream =
+      reinterpret_cast<PulseAudioInputStream*>(user_data);
+  stream->device_name_ = info->default_source_name;

[Henrik Grunell, 2016/03/07 11:37:17]

Same here as for output (see that comment), add a new member variable and don't
change |devcie_name_|.

[rchtara, 2016/03/08 17:28:16]

Done.

+  pa_threaded_mainloop* pa_mainloop =
+      static_cast<pa_threaded_mainloop*>(stream->pa_mainloop_);
+  pa_threaded_mainloop_signal(pa_mainloop, 0);
+}
+
+void PulseAudioInputStream::UseSystemDefaultInputDevice() {
+  DCHECK(pa_mainloop_);
+  DCHECK(pa_context_);
+  pa_operation* operation = pa_context_get_server_info(
+      pa_context_, PulseAudioInputStream::UseSystemDefaultInputDeviceCallback,
+      this);
+  WaitForOperationCompletion(pa_mainloop_, operation);
+}
+
 bool PulseAudioInputStream::Open() {
   DCHECK(thread_checker_.CalledOnValidThread());
   AutoPulseLock auto_lock(pa_mainloop_);
+
+  if (device_name_ == AudioManagerBase::kDefaultDeviceId) {
+    UseSystemDefaultInputDevice();

[Henrik Grunell, 2016/03/07 11:37:17]

Should this function be called under the lock?

[rchtara, 2016/03/08 17:28:16]

I'm not sure, it works even the lock is completely removed. But I'm dont feel
comfortable about removing it as it's used in start,stop...

+  }
+
   if (!pulse::CreateInputStream(pa_mainloop_, pa_context_, &handle_, params_,
                                 device_name_, &StreamNotifyCallback, this)) {
     return false;