Add logging to debug Fabric diffing algorithm

Reviewed By: achen1

Differential Revision: D7319185

fbshipit-source-id: fe47c21db5e1415aebe806f0d74b1f65f667a397

ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewAtIndex.java

@@ -28,4 +28,9 @@ public class ViewAtIndex {
     mTag = tag;
     mIndex = index;
   }
+
+  @Override
+  public String toString() {
+    return "[" + mIndex + ", " + mTag + "]";
+  }
 }