Use simulcast for screenshare only in conference mode

webrtc/video/vie_encoder.cc

 /*
  *  Copyright (c) 2012 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 419 matching lines @@
   codec.startBitrate =
       std::max(encoder_start_bitrate_bps_ / 1000, codec.minBitrate);
   codec.startBitrate = std::min(codec.startBitrate, codec.maxBitrate);
   codec.expect_encode_from_texture = last_frame_info_->is_texture;
 
   bool success = video_sender_.RegisterSendCodec(
                      &codec, number_of_cores_,
                      static_cast<uint32_t>(max_data_payload_length_)) == VCM_OK;
   if (!success) {
     LOG(LS_ERROR) << "Failed to configure encoder.";
-    RTC_DCHECK(success);
+    rate_allocator_.reset();
   }
 
   video_sender_.UpdateChannelParemeters(rate_allocator_.get(),
                                         bitrate_observer_);
 
   int framerate = stats_proxy_->GetSendFrameRate();
   if (framerate == 0)
     framerate = codec.maxFramerate;
   stats_proxy_->OnEncoderReconfigured(
-      encoder_config_, rate_allocator_->GetPreferredBitrateBps(framerate));
+      encoder_config_, rate_allocator_.get()
+                           ? rate_allocator_->GetPreferredBitrateBps(framerate)
+                           : codec.maxBitrate);
 
   pending_encoder_reconfiguration_ = false;
 
   sink_->OnEncoderConfigurationChanged(
       std::move(streams), encoder_config_.min_transmit_bitrate_bps);
 
   ConfigureQualityScaler();
 }
 
 void ViEEncoder::ConfigureQualityScaler() {
@@ skipping 347 matching lines @@
   --scale_counter_[reason];
   source_proxy_->RequestHigherResolutionThan(current_pixel_count);
   LOG(LS_INFO) << "Scaling up resolution.";
   for (size_t i = 0; i < kScaleReasonSize; ++i) {
     LOG(LS_INFO) << "Scaled " << scale_counter_[i]
                  << " times for reason: " << (i ? "cpu" : "quality");
   }
 }
 
 }  // namespace webrtc