Introduce AudioHardwareConfig for renderer side audio device info.

content/renderer/media/audio_message_filter.cc

Index: content/renderer/media/audio_message_filter.cc
diff --git a/content/renderer/media/audio_message_filter.cc b/content/renderer/media/audio_message_filter.cc
index 22915c521c53264ededd36610bf119e14089c95c..3c2c964619789c2a0281e7b98a6f504cc365510d 100644
--- a/content/renderer/media/audio_message_filter.cc
+++ b/content/renderer/media/audio_message_filter.cc
@@ -8,7 +8,9 @@
 #include "base/message_loop.h"
 #include "base/time.h"
 #include "content/common/child_process.h"
+#include "content/common/child_thread.h"
 #include "content/common/media/audio_messages.h"
+#include "content/renderer/media/renderer_audio_hardware_config.h"
 #include "content/renderer/render_thread_impl.h"
 #include "ipc/ipc_logging.h"
 
@@ -96,6 +98,7 @@ bool AudioMessageFilter::OnMessageReceived(const IPC::Message& message) {
   IPC_BEGIN_MESSAGE_MAP(AudioMessageFilter, message)
     IPC_MESSAGE_HANDLER(AudioMsg_NotifyStreamCreated, OnStreamCreated)
     IPC_MESSAGE_HANDLER(AudioMsg_NotifyStreamStateChanged, OnStreamStateChanged)
+    IPC_MESSAGE_HANDLER(AudioMsg_NotifyDeviceChanged, OnOutputDeviceChanged)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
@@ -177,4 +180,23 @@ void AudioMessageFilter::OnStreamStateChanged(
     it->second->OnStateChanged(state);
 }
 
+void AudioMessageFilter::OnOutputDeviceChanged(int stream_id,
+                                               int new_buffer_size,
+                                               int new_sample_rate) {
+  if (MessageLoop::current() != ChildThread::current()->message_loop()) {

[henrika (OOO until Aug 14), 2013/01/29 10:46:49]

Please add add a comment on why this part is needed. ChildThread::current()
isn't that intuitive if you ask me.

[DaleCurtis, 2013/01/29 19:36:00]

Yeah, I don't really like the way this is currently, it obviates the
"on-any-thread" property of AudioHardwareConfig in a bad way.  I'd prefer if
AudioMessageFilter already had a pointer to the AudioHardwareConfig by this
point. However we don't want a synchronous IPC issued during construction of
AudioMessageFilter (and thus RenderThreadImpl).

[DaleCurtis, 2013/01/30 01:31:06]

Removed all this in favor of having RenderThreadImpl provide the
RendererAudioHardwareConfig when created. This avoids any weird ChildThread
stuff.

+    ChildThread::current()->message_loop()->PostTask(FROM_HERE, base::Bind(
+        &AudioMessageFilter::OnOutputDeviceChanged, this,
+        stream_id, new_buffer_size, new_sample_rate));
+    return;
+  }
+
+  DelegateMap::const_iterator it = delegates_.find(stream_id);

[miu, 2013/01/29 04:55:43]

Need to use delegates_lock_ here for thread-safety (see other OnXXX() methods).

[DaleCurtis, 2013/01/30 01:31:06]

Removed since this function doesn't really need that.

+  DLOG_IF(WARNING, it == delegates_.end())
+      << "No delegate found for device change. ";
+  if (it != delegates_.end()) {
+    RenderThreadImpl::current()->GetAudioHardwareConfig()->UpdateOutputConfig(

[henrika (OOO until Aug 14), 2013/01/29 10:46:49]

I always use DCHECK in these types of situations. 

[DaleCurtis, 2013/01/30 01:31:06]

Removed.

+        new_buffer_size, new_sample_rate);
+  }
+}
+
 }  // namespace content