Cast: Don't create threads for each CastSessionDelegate

chrome/renderer/media/cast_threads.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Manages threads used by Cast Streaming Extensions API. There is a
+// singleton object of this class in the renderer.
+//
+// There are two threads owned by this class:
+// 1. Audio encode thread.
+// 2. Video encode thread.
+// These two threads are started when the first CastSessionDelegate is
+// created. When the last CastSessionDelegate is destroyed these threads
+// are stopped.
+
+#ifndef CHROME_RENDERER_MEDIA_CAST_THREADS_H_
+#define CHROME_RENDERER_MEDIA_CAST_THREADS_H_
+
+#include "base/threading/thread.h"
+
+class CastThreads {
+ public:
+  CastThreads();

[scherkus (not reviewing), 2014/02/21 22:01:03]

these can be made private and have something like:

friend struct base::DefaultLazyInstanceTraits<CastThreads>;

[Alpha Left Google, 2014/02/22 01:04:34]

Done.

+  ~CastThreads();
+
+  // IncrementUsage() is called when a CastSessionDelegate is created in
+  // the renderer. When CastSessionDelegate is being destroyed it calls
+  // DecrementUsage().
+  // The first call to IncrementUsage() will start both audio and video
+  // encode threads. The last call to DecrementUsage() will stop these
+  // two threads.
+  void IncrementUsage();

[scherkus (not reviewing), 2014/02/21 22:01:03]

it might be overkill ... but you could declare a helper class that tracks usage

or perhaps it's not even worth cleaning up the threads after they've been
created seeing that this is a renderer process and will eventually get nuked

WDYT?

[Alpha Left Google, 2014/02/22 01:04:34]

Okay I just create threads then this CastThreads is constructed.

+  void DecrementUsage();
+
+  scoped_refptr<base::MessageLoopProxy> GetAudioEncodeMessageLoopProxy();
+  scoped_refptr<base::MessageLoopProxy> GetVideoEncodeMessageLoopProxy();
+
+ private:
+  int use_count_;
+  base::Thread audio_encode_thread_;
+  base::Thread video_encode_thread_;
+};

[scherkus (not reviewing), 2014/02/21 22:01:03]

DISALLOW etc...

[Alpha Left Google, 2014/02/22 01:04:34]

Done.

+
+#endif  // CHROME_RENDERER_MEDIA_CAST_THREADS_H_