Candidate fix for a crash at shutdown when the IO thread is going away. More details in the bug rep…

media/audio/audio_output_device.cc

 // Copyright (c) 2012 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 "media/audio/audio_output_device.h"
 
 #include "base/debug/trace_event.h"
 #include "base/message_loop.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/time.h"
@@ skipping 124 matching lines @@
   }
 }
 
 void AudioOutputDevice::ShutDownOnIOThread() {
   DCHECK(message_loop()->BelongsToCurrentThread());
 
   // Make sure we don't call shutdown more than once.
   if (stream_id_) {
     is_started_ = false;
 
-    ipc_->CloseStream(stream_id_);
-    ipc_->RemoveDelegate(stream_id_);
+    if (ipc_) {
+      ipc_->CloseStream(stream_id_);
+      ipc_->RemoveDelegate(stream_id_);
+    }
+
     stream_id_ = 0;
   }
 
   // We can run into an issue where ShutDownOnIOThread is called right after
   // OnStreamCreated is called in cases where Start/Stop are called before we
   // get the OnStreamCreated callback.  To handle that corner case, we call
   // Stop(). In most cases, the thread will already be stopped.
   // Another situation is when the IO thread goes away before Stop() is called
   // in which case, we cannot use the message loop to close the thread handle
   // and can't not rely on the main thread existing either.
@@ skipping 114 matching lines @@
   // conversions that happen in the <audio> and WebRTC scenarios.
   InterleaveFloatToInt(audio_data_, shared_memory_.memory(),
       num_frames, audio_parameters_.bits_per_sample() / 8);
 
   // Let the host know we are done.
   SetActualDataSizeInBytes(&shared_memory_, memory_length_,
       num_frames * audio_parameters_.GetBytesPerFrame());
 }
 
 }  // namespace media.