[ESLint] Fix violations when enabling curly rule in eslint.

tracing/tracing/model/selectable_item.html

Index: tracing/tracing/model/selectable_item.html
diff --git a/tracing/tracing/model/selectable_item.html b/tracing/tracing/model/selectable_item.html
index 446d9214715d662bf567d63e8421eae798291132..7f7dd01421ea7d3258d2daf98c565f6e250ff665 100644
--- a/tracing/tracing/model/selectable_item.html
+++ b/tracing/tracing/model/selectable_item.html
@@ -39,15 +39,13 @@ tr.exportTo('tr.model', function() {
 
     addToSelection: function(selection) {
       var modelItem = this.modelItem_;
-      if (!modelItem)
-        return;
+      if (!modelItem) return;
       selection.push(modelItem);
     },
 
     addToTrackMap: function(eventToTrackMap, track) {
       var modelItem = this.modelItem_;
-      if (!modelItem)
-        return;
+      if (!modelItem) return;
       eventToTrackMap.addEvent(modelItem, track);
     }
   };