Part 1: Plumb render view ID to render host

media/audio/audio_output_device.cc

Index: media/audio/audio_output_device.cc
diff --git a/media/audio/audio_output_device.cc b/media/audio/audio_output_device.cc
index d432103ce06112cc8fda0a0575fb3f39545ed416..06c70bac1e2a64aa9dffe27830f7d95acf8c0315 100644
--- a/media/audio/audio_output_device.cc
+++ b/media/audio/audio_output_device.cc
@@ -44,7 +44,7 @@ AudioOutputDevice::AudioOutputDevice(
       stream_id_(0),
       play_on_start_(true),
       is_started_(false) {
-  CHECK(ipc_);
+  CHECK(ipc_.get());
 }
 
 void AudioOutputDevice::Initialize(const AudioParameters& params,
@@ -222,7 +222,7 @@ void AudioOutputDevice::OnStreamCreated(
 }
 
 void AudioOutputDevice::OnIPCClosed() {
-  ipc_ = NULL;
+  ipc_.reset();
 }
 
 void AudioOutputDevice::WillDestroyCurrentMessageLoop() {