Re-land r207105 (Mac audio capture threading fix) with unit test memory leak issue resolved.

content/browser/renderer_host/media/audio_input_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_input_renderer_host.h"
 
 #include "base/bind.h"
 #include "base/metrics/histogram.h"
 #include "base/process.h"
 #include "base/shared_memory.h"
@@ skipping 252 matching lines @@
   if (!writer->Init()) {
     SendErrorMessage(stream_id);
     return;
   }
 
   // If we have successfully created the SyncWriter then assign it to the
   // entry and construct an AudioInputController.
   entry->writer.reset(writer.release());
   if (WebContentsCaptureUtil::IsWebContentsDeviceId(device_id)) {
     entry->controller = media::AudioInputController::CreateForStream(
-        audio_manager_->GetWorkerLoop(),
+        audio_manager_->GetMessageLoop(),
         this,
         WebContentsAudioInputStream::Create(
             device_id, audio_params, audio_manager_->GetWorkerLoop(),
             audio_mirroring_manager_),
         entry->writer.get());
   } else {
     // TODO(henrika): replace CreateLowLatency() with Create() as soon
     // as satish has ensured that Speech Input also uses the default low-
     // latency path. See crbug.com/112472 for details.
     entry->controller = media::AudioInputController::CreateLowLatency(
@@ skipping 114 matching lines @@
   // TODO(hclam): Implement a faster look up method.
   for (AudioEntryMap::iterator i = audio_entries_.begin();
        i != audio_entries_.end(); ++i) {
     if (controller == i->second->controller.get())
       return i->second;
   }
   return NULL;
 }
 
 }  // namespace content