Winscope: fix layer traversal

Test: open sf trace of chrome in winscope
Change-Id: I4e0e9fad427e920021e00a2d6330027b43543502
diff --git a/tools/winscope/src/sf_visibility.js b/tools/winscope/src/sf_visibility.js
index af5c16f..11ff0cd 100644
--- a/tools/winscope/src/sf_visibility.js
+++ b/tools/winscope/src/sf_visibility.js
@@ -281,7 +281,7 @@
             `Children layer with id ${id} not found in dumped layers... ` +
             `Skipping layer in traversal...`);
       } else {
-        relatives.push(layerMap[id]);
+        children.push(layerMap[id]);
       }
     }