Fixing crash that may occur after destroying a VideoSendStream.

webrtc/video/video_send_stream.cc

Index: webrtc/video/video_send_stream.cc
diff --git a/webrtc/video/video_send_stream.cc b/webrtc/video/video_send_stream.cc
index 21a22dc9143203aaf075f2bab2adfe13a7029442..555b68c94d6ef47e5fa371e4533fd3e123c07c85 100644
--- a/webrtc/video/video_send_stream.cc
+++ b/webrtc/video/video_send_stream.cc
@@ -449,7 +449,6 @@ VideoSendStream::VideoSendStream(
 VideoSendStream::~VideoSendStream() {
   LOG(LS_INFO) << "~VideoSendStream: " << config_.ToString();
 
-  bitrate_allocator_->RemoveObserver(this);
   Stop();
 
   // Stop the encoder thread permanently.
@@ -457,6 +456,10 @@ VideoSendStream::~VideoSendStream() {
   encoder_wakeup_event_.Set();
   encoder_thread_.Stop();
 
+  // This needs to happen after stopping the encoder thread,
+  // since the encoder thread calls AddObserver.
+  bitrate_allocator_->RemoveObserver(this);
+
   module_process_thread_->DeRegisterModule(&overuse_detector_);
   vie_channel_.RegisterSendFrameCountObserver(nullptr);
   vie_channel_.RegisterSendBitrateObserver(nullptr);