Screen content simulcast layers should not be downscaled.

webrtc/media/engine/simulcast.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 212 matching lines @@
     } else {
       streams[s].temporal_layer_thresholds_bps.resize(
           kDefaultConferenceNumberOfTemporalLayers[s] - 1);
       streams[s].max_bitrate_bps = FindSimulcastMaxBitrateBps(width, height);
       streams[s].target_bitrate_bps =
           FindSimulcastTargetBitrateBps(width, height);
       streams[s].min_bitrate_bps = FindSimulcastMinBitrateBps(width, height);
       streams[s].max_framerate = max_framerate;
     }
 
-    width /= 2;
-    height /= 2;
+    if (!is_screencast) {
+      width /= 2;
+      height /= 2;
+    }
     if (s == 0)
       break;
   }
 
   // Spend additional bits to boost the max stream.
   int bitrate_left_bps = max_bitrate_bps - GetTotalMaxBitrateBps(streams);
   if (bitrate_left_bps > 0) {
     streams.back().max_bitrate_bps += bitrate_left_bps;
   }
 
@@ skipping 50 matching lines @@
 
   return true;
 }
 
 bool UseSimulcastScreenshare() {
   return webrtc::field_trial::FindFullName(
              kSimulcastScreenshareFieldTrialName) == "Enabled";
 }
 
 }  // namespace cricket