Add field trial for balanced degradation preference.

webrtc/video_send_stream.h

Index: webrtc/video_send_stream.h
diff --git a/webrtc/video_send_stream.h b/webrtc/video_send_stream.h
index 45d1a55365f04abb60a3a3576d992bf33a8a482a..266112e5871550d9406a945981647724170d1bfa 100644
--- a/webrtc/video_send_stream.h
+++ b/webrtc/video_send_stream.h
@@ -224,9 +224,9 @@ class VideoSendStream {
   enum class DegradationPreference {
     // Don't take any actions based on over-utilization signals.
     kDegradationDisabled,
-    // On over-use, request lost resolution, possibly causing down-scaling.
+    // On over-use, request lower frame rate, possibly causing frame drops.
     kMaintainResolution,
-    // On over-use, request lower frame rate, possible causing frame drops.
+    // On over-use, request lower resolution, possibly causing down-scaling.
     kMaintainFramerate,
     // Try to strike a "pleasing" balance between frame rate or resolution.
     kBalanced,