Recreate WebrtcVideoSendStream if screen content setting is changed.

webrtc/media/engine/webrtcvideoengine2.cc

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 1594 matching lines @@
     rtc::VideoSourceInterface<webrtc::VideoFrame>* source) {
   TRACE_EVENT0("webrtc", "WebRtcVideoSendStream::SetVideoSend");
   RTC_DCHECK_RUN_ON(&thread_checker_);
 
   // Ignore |options| pointer if |enable| is false.
   bool options_present = enable && options;
 
   if (options_present) {
     VideoOptions old_options = parameters_.options;
     parameters_.options.SetAll(*options);
-    if (parameters_.options != old_options) {
+    if (parameters_.options.is_screencast.value_or(false) !=
+        old_options.is_screencast.value_or(false)) {
+      // If screen content settings change, we may need to recreate the
+      // stream so that the correct encoder is created.

[pthatcher1, 2017/02/21 23:00:34]

This could use a little more detail about why it's necessary.

+      RecreateWebRtcStream();
+    } else {

[pthatcher1, 2017/02/21 23:00:34]

Shouldn't this be "else if (parameters_.options != old_options)" ?  Otherwise,
we'd reconfigure even if the options didn't change.

[Taylor Brandstetter, 2017/02/22 00:27:24]

+1

[sprang_webrtc, 2017/02/22 15:53:04]

Yes, I screwed up copy/paste from a chromium checkout where I was iterating and
testing...

       ReconfigureEncoder();
     }
   }
 
   if (source_ && stream_) {
     stream_->SetSource(
         nullptr, webrtc::VideoSendStream::DegradationPreference::kBalanced);
   }
   // Switch to the new source.
   source_ = source;
@@ skipping 901 matching lines @@
         rtx_mapping[video_codecs[i].codec.id] !=
             ulpfec_config.red_payload_type) {
       video_codecs[i].rtx_payload_type = rtx_mapping[video_codecs[i].codec.id];
     }
   }
 
   return video_codecs;
 }
 
 }  // namespace cricket