Reorder AudioMessageFilter shutdown. Remove spammy DCHECK.

content/renderer/media/audio_renderer_mixer_manager.cc

 // Copyright (c) 2012 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 "content/renderer/media/audio_renderer_mixer_manager.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "content/renderer/media/audio_device_factory.h"
 #include "media/audio/audio_output_device.h"
 #include "media/base/audio_hardware_config.h"
 #include "media/base/audio_renderer_mixer.h"
 #include "media/base/audio_renderer_mixer_input.h"
 
 namespace content {
 
 AudioRendererMixerManager::AudioRendererMixerManager(
     media::AudioHardwareConfig* hardware_config)
     : hardware_config_(hardware_config),
       sink_for_testing_(NULL) {
 }
 
 AudioRendererMixerManager::~AudioRendererMixerManager() {
-  DCHECK(mixers_.empty());
+  // References to AudioRendererMixers may be owned by garbage collected
+  // objects.  During process shutdown they may be leaked, so, transitively,
+  // |mixers_| may leak (i.e., may be non-empty at this time) as well.
 }
 
 media::AudioRendererMixerInput* AudioRendererMixerManager::CreateInput(
     int source_render_view_id, int source_render_frame_id) {
   return new media::AudioRendererMixerInput(
       base::Bind(
           &AudioRendererMixerManager::GetMixer, base::Unretained(this),
           source_render_view_id,
           source_render_frame_id),
       base::Bind(
@@ skipping 65 matching lines @@
 
   // Only remove the mixer if AudioRendererMixerManager is the last owner.
   it->second.ref_count--;
   if (it->second.ref_count == 0) {
     delete it->second.mixer;
     mixers_.erase(it);
   }
 }
 
 }  // namespace content