Revert of Revert of Remove the last piece of deprecated synchronous IO code.

content/browser/renderer_host/media/audio_renderer_host.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/browser/renderer_host/media/audio_renderer_host.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/memory/shared_memory.h"
 #include "base/metrics/histogram.h"
@@ skipping 339 matching lines @@
   // Initialize the |output_device_id| to an empty string which indicates that
   // the default device should be used. If a StreamDeviceInfo instance was found
   // though, then we use the matched output device.
   std::string output_device_id;
   const StreamDeviceInfo* info = media_stream_manager_->
       audio_input_device_manager()->GetOpenedDeviceInfoById(session_id);
   if (info)
     output_device_id = info->device.matched_output_device_id;
 
   // Create the shared memory and share with the renderer process.
-  // For synchronized I/O (if input_channels > 0) then we allocate
-  // extra memory after the output data for the input data.
   uint32 shared_memory_size = AudioBus::CalculateMemorySize(params);
   scoped_ptr<base::SharedMemory> shared_memory(new base::SharedMemory());
   if (!shared_memory->CreateAndMapAnonymous(shared_memory_size)) {
     SendErrorMessage(stream_id);
     return;
   }
 
   scoped_ptr<AudioSyncReader> reader(
       new AudioSyncReader(shared_memory.get(), params));
   if (!reader->Init()) {
@@ skipping 126 matching lines @@
 
   AudioEntryMap::const_iterator i = audio_entries_.find(stream_id);
   return i != audio_entries_.end() ? i->second : NULL;
 }
 
 bool AudioRendererHost::HasActiveAudio() {
   return !base::AtomicRefCountIsZero(&num_playing_streams_);
 }
 
 }  // namespace content