Cast: Don't create threads for each CastSessionDelegate

chrome/renderer/media/cast_threads.cc

+// 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.
+
+#include "chrome/renderer/media/cast_threads.h"
+
+#include "base/logging.h"
+
+CastThreads::CastThreads()
+    : use_count_(0),
+      audio_encode_thread_("CastAudioEncodeThread"),
+      video_encode_thread_("CastVideoEncodeThread") {}
+
+CastThreads::~CastThreads() { DCHECK(!use_count_); }
+
+void CastThreads::IncrementUsage() {
+  if (++use_count_ == 1) {
+    audio_encode_thread_.Start();
+    video_encode_thread_.Start();
+  }
+}
+
+void CastThreads::DecrementUsage() {
+  if (--use_count_ == 0) {
+    audio_encode_thread_.Stop();
+    video_encode_thread_.Stop();
+  }
+}
+
+scoped_refptr<base::MessageLoopProxy>
+CastThreads::GetAudioEncodeMessageLoopProxy() {
+  return audio_encode_thread_.message_loop_proxy();
+}
+
+scoped_refptr<base::MessageLoopProxy>
+CastThreads::GetVideoEncodeMessageLoopProxy() {
+  return video_encode_thread_.message_loop_proxy();
+}