Add VideoEncoder.ScalingSettings.toString method.

Bug: None
Change-Id: Ib7563bdec49736b104d3cbb52a7c77b6aa142030
Reviewed-on: https://webrtc-review.googlesource.com/70500
Reviewed-by: Paulina Hensman <phensman@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22922}

sdk/android/api/org/webrtc/VideoEncoder.java

@@ -148,6 +148,11 @@ public interface VideoEncoder {
       this.low = low;
       this.high = high;
     }
+
+    @Override
+    public String toString() {
+      return on ? "[ " + low + ", " + high + " ]" : "OFF";
+    }
   }
 
   public interface Callback {