Pass task runners to AudioManager constructor.

media/audio/audio_thread.cc

+// Copyright 2016 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 "media/audio/audio_thread.h"
+
+#include "base/lazy_instance.h"
+
+static base::LazyInstance<media::AudioThread> g_thread =
+    LAZY_INSTANCE_INITIALIZER;
+
+namespace media {
+
+AudioThread::AudioThread() : thread_("Audio") {
+#if defined(OS_WIN)
+  thread_.init_com_with_mta(true);
+#endif
+  CHECK(thread_.Start());
+}
+
+// static
+base::Thread* AudioThread::Get() {
+  return &(g_thread.Get().thread_);
+}
+
+}  // namespace media