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

tracing/tracing/ui/base/info_bar_group.html

Index: tracing/tracing/ui/base/info_bar_group.html
diff --git a/tracing/tracing/ui/base/info_bar_group.html b/tracing/tracing/ui/base/info_bar_group.html
index af82995de014ab54c13dd96de2f41bc48fce6f6d..d083d0bfd98bbf1906b56a76801bc9d9707939bb 100644
--- a/tracing/tracing/ui/base/info_bar_group.html
+++ b/tracing/tracing/ui/base/info_bar_group.html
@@ -35,10 +35,12 @@ Polymer({
   addMessage: function(text, opt_buttons) {
     opt_buttons = opt_buttons || [];
     for (var i = 0; i < opt_buttons.length; i++) {
-      if (opt_buttons[i].buttonText === undefined)
+      if (opt_buttons[i].buttonText === undefined) {
         throw new Error('buttonText must be provided');
-      if (opt_buttons[i].onClick === undefined)
+      }
+      if (opt_buttons[i].onClick === undefined) {
         throw new Error('onClick must be provided');
+      }
     }
 
     this.messages_.push({