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

media/audio/audio_input_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_input_device.h"
 
 #include "base/bind.h"
 #include "base/message_loop.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/time.h"
@@ skipping 235 matching lines @@
   DCHECK(message_loop()->BelongsToCurrentThread());
   if (stream_id_)
     ipc_->RecordStream(stream_id_);
 }
 
 void AudioInputDevice::ShutDownOnIOThread() {
   DCHECK(message_loop()->BelongsToCurrentThread());
   // NOTE: |completion| may be NULL.
   // Make sure we don't call shutdown more than once.
   if (stream_id_) {
-    ipc_->CloseStream(stream_id_);
-    ipc_->RemoveDelegate(stream_id_);
+    if (ipc_) {
+      ipc_->CloseStream(stream_id_);
+      ipc_->RemoveDelegate(stream_id_);
+    }
 
     stream_id_ = 0;
     session_id_ = 0;
     pending_device_ready_ = false;
     agc_is_enabled_ = false;
   }
 
   // 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
@@ skipping 73 matching lines @@
                              number_of_frames);
   }
 
   // Deliver captured data to the client in floating point format
   // and update the audio-delay measurement.
   capture_callback_->Capture(audio_data_, number_of_frames,
                              audio_delay_milliseconds, volume);
 }
 
 }  // namespace media