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

tracing/tracing/ui/base/bar_chart_test.html

Index: tracing/tracing/ui/base/bar_chart_test.html
diff --git a/tracing/tracing/ui/base/bar_chart_test.html b/tracing/tracing/ui/base/bar_chart_test.html
index d628a010ff2a8870d0f0b92dce8c9dadbd349169..cdb98340b4cfa777d7d9e92600ee5b46a58e5313 100644
--- a/tracing/tracing/ui/base/bar_chart_test.html
+++ b/tracing/tracing/ui/base/bar_chart_test.html
@@ -121,8 +121,7 @@ tr.b.unittest.testSuite(function() {
       updateBrushedRange();
     });
     chart.addEventListener('item-mousemove', function(e) {
-      if (e.button === undefined)
-        return;
+      if (e.button === undefined) return;
       curMouseX = e.x;
       updateBrushedRange();
     });