Fix back-to-back StartPlayback/StopPlayback issue in PPAPI IPC proxy

ppapi/shared_impl/ppb_audio_shared.cc

Index: ppapi/shared_impl/ppb_audio_shared.cc
===================================================================
--- ppapi/shared_impl/ppb_audio_shared.cc	(revision 153270)
+++ ppapi/shared_impl/ppb_audio_shared.cc	(working copy)
@@ -29,6 +29,9 @@
 }
 
 PPB_Audio_Shared::~PPB_Audio_Shared() {
+  // Shut down the socket to escape any hanging |Receive|s.
+  if (socket_.get())
+    socket_->Shutdown();
   StopThread();
 }
 
@@ -105,10 +108,7 @@
 }
 
 void PPB_Audio_Shared::StopThread() {
-  // Shut down the socket to escape any hanging |Receive|s.
-  if (socket_.get())
-    socket_->Shutdown();
-  #if !defined(OS_NACL)
+#if !defined(OS_NACL)
   if (audio_thread_.get()) {
     audio_thread_->Join();
     audio_thread_.reset();