Avoid double deleting from |MediaStreamDispatcher::label_stream_map_|.

content/renderer/media/media_stream_dispatcher.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 "content/renderer/media/media_stream_dispatcher.h"
 
 #include <stddef.h>
 
 #include "base/logging.h"
 #include "content/common/media/media_stream_messages.h"
@@ skipping 334 matching lines @@
   }
   Stream* stream = &it->second;
   if (IsAudioInputMediaType(device_info.device.type))
     RemoveStreamDeviceFromArray(device_info, &stream->audio_array);
   else
     RemoveStreamDeviceFromArray(device_info, &stream->video_array);
 
   if (stream->handler.get())
     stream->handler->OnDeviceStopped(label, device_info);
 
+  // |it| could have already been invalidated in the function call above. So we
+  // need to check if |label| is still in |label_stream_map_| again.
+  // Note: this is a quick fix to the crash caused by erasing the invalidated
+  // iterator from |label_stream_map_| (crbug.com/616884). Future work needs to
+  // be done to resolve this re-entering issue.

[miu, 2016/06/04 04:30:01]

s/re-entering/re-entrancy/

[xjz, 2016/06/06 17:09:53]

Done.

+  it = label_stream_map_.find(label);
+  if (it == label_stream_map_.end())
+    return;
+  stream = &it->second;
   if (stream->audio_array.empty() && stream->video_array.empty())
     label_stream_map_.erase(it);
 }
 
 void MediaStreamDispatcher::OnDevicesEnumerated(
     int request_id,
     const StreamDeviceInfoArray& device_array) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK_GE(request_id, 0);
 
@@ skipping 82 matching lines @@
   DCHECK(thread_checker_.CalledOnValidThread());
   LabelStreamMap::iterator it = label_stream_map_.find(label);
   if (it == label_stream_map_.end() ||
       it->second.video_array.size() <= static_cast<size_t>(index)) {
     return StreamDeviceInfo::kNoId;
   }
   return it->second.video_array[index].session_id;
 }
 
 }  // namespace content