Replace more ObserverList with base::ObserverList.

media/audio/audio_manager_base.cc

Index: media/audio/audio_manager_base.cc
diff --git a/media/audio/audio_manager_base.cc b/media/audio/audio_manager_base.cc
index fe7c12e35d5dfae25d4af2c10fb9631969463876..b633432fc0eb43482abed2339803022e9248126b 100644
--- a/media/audio/audio_manager_base.cc
+++ b/media/audio/audio_manager_base.cc
@@ -78,10 +78,11 @@ AudioManagerBase::AudioManagerBase(AudioLogFactory* audio_log_factory)
       max_num_input_streams_(kDefaultMaxInputStreams),
       num_output_streams_(0),
       num_input_streams_(0),
-      // TODO(dalecurtis): Switch this to an ObserverListThreadSafe, so we don't
+      // TODO(dalecurtis): Switch this to an base::ObserverListThreadSafe, so we
+      // don't
       // block the UI thread when swapping devices.
       output_listeners_(
-          ObserverList<AudioDeviceListener>::NOTIFY_EXISTING_ONLY),
+          base::ObserverList<AudioDeviceListener>::NOTIFY_EXISTING_ONLY),
       audio_thread_("AudioThread"),
       audio_log_factory_(audio_log_factory) {
 #if defined(OS_WIN)