Fix a memory leak caused by AudioRenedererHost.

chrome/browser/renderer_host/audio_renderer_host_unittest.cc

 // Copyright (c) 2009 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 "base/message_loop.h"
 #include "base/process.h"
 #include "base/scoped_ptr.h"
 #include "chrome/browser/renderer_host/audio_renderer_host.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 class AudioRendererHostTest : public testing::Test {
  protected:
   virtual void SetUp() {
     // Create a message loop so AudioRendererHost can use it.
     message_loop_.reset(new MessageLoop(MessageLoop::TYPE_IO));
-    host_ = new AudioRendererHost(MessageLoop::current());
+    host_ = new AudioRendererHost(message_loop_.get());
   }
 
   virtual void TearDown() {
+    // This task post a task to message_loop_ to do internal destruction on
+    // message_loop_.
     host_->Destroy();
+    // We need to continue running message_loop_ to complete all destructions. 
+    message_loop_->RunAllPending();
   }
 
   scoped_refptr<AudioRendererHost> host_;
   scoped_ptr<MessageLoop> message_loop_;
 };
 
 TEST_F(AudioRendererHostTest, NoTest) {
   // TODO(hclam): come up with useful tests.
 }