Pass task runners to AudioManager constructor.

components/audio_modem/BUILD.gn

 # Copyright 2015 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.
 
 source_set("audio_modem") {
   sources = [
     "audio_modem_switches.cc",
     "audio_modem_switches.h",
     "audio_player.h",
     "audio_player_impl.cc",
@@ skipping 45 matching lines @@
     "audio_player_unittest.cc",
     "audio_recorder_unittest.cc",
     "modem_unittest.cc",
   ]
 
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   deps = [
     ":test_support",
     "//base",
+    "//base/test:test_support",
     "//content/test:test_support",
     "//media",
     "//media:shared_memory_support",
     "//testing/gtest",
   ]
 }