Merge to 57: Screen content simulcast layers should not be downscaled.

webrtc/media/engine/simulcast.cc

Index: webrtc/media/engine/simulcast.cc
diff --git a/webrtc/media/engine/simulcast.cc b/webrtc/media/engine/simulcast.cc
index d0dafc908dee2514dc261a8b90c4505cf1a01e82..74d3e52a869c4a6047f6349e64ec2db50c88c378 100644
--- a/webrtc/media/engine/simulcast.cc
+++ b/webrtc/media/engine/simulcast.cc
@@ -231,8 +231,10 @@ std::vector<webrtc::VideoStream> GetSimulcastConfig(size_t max_streams,
       streams[s].max_framerate = max_framerate;
     }
 
-    width /= 2;
-    height /= 2;
+    if (!is_screencast) {
+      width /= 2;
+      height /= 2;
+    }
     if (s == 0)
       break;
   }