Convert some audio code to OnceCallback.

media/mojo/services/mojo_audio_output_stream_provider.cc

Index: media/mojo/services/mojo_audio_output_stream_provider.cc
diff --git a/media/mojo/services/mojo_audio_output_stream_provider.cc b/media/mojo/services/mojo_audio_output_stream_provider.cc
index 10f8c89d4d7d797bd5bca401d07f92c73d396112..d27f4187175bfc5faedd286e534225de0cd3d124 100644
--- a/media/mojo/services/mojo_audio_output_stream_provider.cc
+++ b/media/mojo/services/mojo_audio_output_stream_provider.cc
@@ -14,9 +14,10 @@ MojoAudioOutputStreamProvider::MojoAudioOutputStreamProvider(
     DeleterCallback deleter_callback)
     : binding_(this, std::move(request)),
       create_delegate_callback_(std::move(create_delegate_callback)),
-      deleter_callback_(base::Bind(std::move(deleter_callback), this)) {
+      deleter_callback_(std::move(deleter_callback)) {
   DCHECK(thread_checker_.CalledOnValidThread());
-  binding_.set_connection_error_handler(deleter_callback_);
+  binding_.set_connection_error_handler(base::Bind(
+      &MojoAudioOutputStreamProvider::OnError, base::Unretained(this)));

[xhwang, 2017/05/15 17:50:55]

Can you add a comment why this base::Unretained(this) is safe?

[Max Morin, 2017/05/16 07:27:34]

Done.

   DCHECK(create_delegate_callback_);
   DCHECK(deleter_callback_);
 }
@@ -33,14 +34,21 @@ void MojoAudioOutputStreamProvider::Acquire(
   if (audio_output_) {
     LOG(ERROR) << "Output acquired twice.";
     binding_.Unbind();
-    deleter_callback_.Run();  // deletes |this|.
+    std::move(deleter_callback_).Run(this);  // deletes |this|.
     return;
   }
 
   audio_output_.emplace(
       std::move(stream_request),
       base::BindOnce(std::move(create_delegate_callback_), params),
-      std::move(callback), deleter_callback_);
+      std::move(callback),
+      base::BindOnce(&MojoAudioOutputStreamProvider::OnError,
+                     base::Unretained(this)));

[xhwang, 2017/05/15 17:50:55]

ditto

[Max Morin, 2017/05/16 07:27:34]

Done.

+}
+
+void MojoAudioOutputStreamProvider::OnError() {
+  // Deletes |this|:
+  std::move(deleter_callback_).Run(this);
 }
 
 }  // namespace media