Bug 621430. Lazily create stream writer thread so we don't create one when using local audio. Also, shut down the stream writer thread when the audio stream dies. r=dougt,a=blocker

content/media/nsAudioStream.cpp

@@ -301,10 +301,12 @@ void nsAudioStream::ShutdownLibrary()
 {
 }
 
-
 nsIThread *
 nsAudioStream::GetThread()
 {
+  if (!mAudioPlaybackThread) {
+    NS_NewThread(getter_AddRefs(mAudioPlaybackThread));
+  }
   return mAudioPlaybackThread;
 }
 
@@ -318,6 +320,23 @@ nsAudioStream* nsAudioStream::AllocateStream()
   return new nsAudioStreamLocal();
 }
 
+class AsyncShutdownPlaybackThread : public nsRunnable
+{
+public:
+  AsyncShutdownPlaybackThread(nsIThread* aThread) : mThread(aThread) {}
+  NS_IMETHODIMP Run() { return mThread->Shutdown(); }
+private:
+  nsCOMPtr<nsIThread> mThread;
+};
+
+nsAudioStream::~nsAudioStream()
+{
+  if (mAudioPlaybackThread) {
+    nsCOMPtr<nsIRunnable> event = new AsyncShutdownPlaybackThread(mAudioPlaybackThread);
+    NS_DispatchToMainThread(event);
+  }
+}
+
 nsAudioStreamLocal::nsAudioStreamLocal() :
   mVolume(1.0),
   mAudioHandle(0),
@@ -327,12 +346,6 @@ nsAudioStreamLocal::nsAudioStreamLocal() :
   mPaused(PR_FALSE),
   mInError(PR_FALSE)
 {
-#ifdef MOZ_IPC
-  // We only need this thread in the main process.
-  if (XRE_GetProcessType() == GeckoProcessType_Default) {
-    NS_NewThread(getter_AddRefs(mAudioPlaybackThread));
-  }
-#endif
 }
 
 nsAudioStreamLocal::~nsAudioStreamLocal()

content/media/nsAudioStream.h

@@ -54,6 +54,8 @@ public:
     FORMAT_FLOAT32
   };
 
+  virtual ~nsAudioStream();
+
   // Initialize Audio Library. Some Audio backends require initializing the
   // library before using it. 
   static void InitLibrary();
@@ -64,7 +66,7 @@ public:
 
   // Thread, usually for MOZ_IPC handling, that is shared between audio streams.
   // This may return null in the child process
-  virtual nsIThread *GetThread();
+  nsIThread *GetThread();
 
   // AllocateStream will return either a local stream or a remoted stream
   // depending on where you call it from.  If MOZ_IPC is enabled, and you