Fix a memory leak caused by AudioRenedererHost.

chrome/browser/renderer_host/audio_renderer_host_unittest.cc

Index: chrome/browser/renderer_host/audio_renderer_host_unittest.cc
diff --git a/chrome/browser/renderer_host/audio_renderer_host_unittest.cc b/chrome/browser/renderer_host/audio_renderer_host_unittest.cc
index d7ab83106f5aa65fea9f2ed893e3107acaec5184..2942dac60778712696f7d53bece77ff4a872d431 100644
--- a/chrome/browser/renderer_host/audio_renderer_host_unittest.cc
+++ b/chrome/browser/renderer_host/audio_renderer_host_unittest.cc
@@ -13,11 +13,15 @@ class AudioRendererHostTest : public testing::Test {
   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_;