Always clear callback after WaveOut Stop().

If an error occurs after Stop() the callback may be destroyed, yet
the callback value was not cleared.  During Close() stop may be called
again, if an error occurs the free'd callback will be notified of the
error...

BUG=none
TEST=none

Review URL: https://codereview.chromium.org/115523010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243649 0039d316-1c4b-4281-b951-d872f2087c98

media/audio/win/waveout_output_win.cc

@@ -248,39 +248,25 @@ void PCMWaveOutAudioOutputStream::Stop() {
   state_ = PCMA_STOPPING;
   base::subtle::MemoryBarrier();
 
-  // Stop watching for buffer event, wait till all the callbacks are complete.
-  // Should be done before ::waveOutReset() call to avoid race condition when
-  // callback that is currently active and already checked that stream is still
-  // being played calls ::waveOutWrite() after ::waveOutReset() returns, later
-  // causing ::waveOutClose() to fail with WAVERR_STILLPLAYING.
-  // TODO(enal): that delays actual stopping of playback. Alternative can be
-  //             to call ::waveOutReset() twice, once before
-  //             ::UnregisterWaitEx() and once after.
+  // Stop watching for buffer event, waits until outstanding callbacks finish.
   if (waiting_handle_) {
-    if (!::UnregisterWaitEx(waiting_handle_, INVALID_HANDLE_VALUE)) {
-      state_ = PCMA_PLAYING;
-      HandleError(MMSYSERR_ERROR);
-      return;
-    }
+    if (!::UnregisterWaitEx(waiting_handle_, INVALID_HANDLE_VALUE))
+      HandleError(::GetLastError());
     waiting_handle_ = NULL;
   }
 
   // Stop playback.
   MMRESULT res = ::waveOutReset(waveout_);
-  if (res != MMSYSERR_NOERROR) {
-    state_ = PCMA_PLAYING;
+  if (res != MMSYSERR_NOERROR)
     HandleError(res);
-    return;
-  }
 
   // Wait for lock to ensure all outstanding callbacks have completed.
   base::AutoLock auto_lock(lock_);
 
   // waveOutReset() leaves buffers in the unpredictable state, causing
   // problems if we want to close, release, or reuse them. Fix the states.
-  for (int ix = 0; ix != num_buffers_; ++ix) {
+  for (int ix = 0; ix != num_buffers_; ++ix)
     GetBuffer(ix)->dwFlags = WHDR_PREPARED;
-  }
 
   // Don't use callback after Stop().
   callback_ = NULL;