Reland: Pass task runners to AudioManager constructor.

media/mojo/services/mojo_media_client.h

Index: media/mojo/services/mojo_media_client.h
diff --git a/media/mojo/services/mojo_media_client.h b/media/mojo/services/mojo_media_client.h
index eb923e2a940d8eb4dcd9ac7eaaf3bd00a537d36b..d64c06cdd9cc0a44d8e01df7f405b008e4245c47 100644
--- a/media/mojo/services/mojo_media_client.h
+++ b/media/mojo/services/mojo_media_client.h
@@ -32,6 +32,10 @@ class MojoMediaClient {
 
   // Called exactly once before any other method.
   virtual void Initialize();
+  // Called before the host application is scheduled to quit.
+  // The application message loop is still valid at this point, so all clean
+  // up tasks requiring the message loop must be completed before returning.
+  virtual void WillQuit();
 
   virtual std::unique_ptr<AudioDecoder> CreateAudioDecoder(
       scoped_refptr<base::SingleThreadTaskRunner> task_runner);