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

tracing/tracing/ui/extras/side_panel/alerts_side_panel.html

Index: tracing/tracing/ui/extras/side_panel/alerts_side_panel.html
diff --git a/tracing/tracing/ui/extras/side_panel/alerts_side_panel.html b/tracing/tracing/ui/extras/side_panel/alerts_side_panel.html
index 344b5580db2f9eaea4c967d2af6675ed7db5d734..6e6b689533de4df5a7865d47b7439f57b9866c47 100644
--- a/tracing/tracing/ui/extras/side_panel/alerts_side_panel.html
+++ b/tracing/tracing/ui/extras/side_panel/alerts_side_panel.html
@@ -85,8 +85,9 @@ Polymer({
   alertsByType_: function(alerts) {
     var alertsByType = {};
     alerts.forEach(function(alert) {
-      if (!alertsByType[alert.title])
+      if (!alertsByType[alert.title]) {
         alertsByType[alert.title] = [];
+      }
 
       alertsByType[alert.title].push(alert);
     });
@@ -126,8 +127,9 @@ Polymer({
     table.selectionMode = tr.ui.b.TableFormat.SelectionMode.ROW;
     table.addEventListener('selection-changed', function(e) {
       var row = table.selectedTableRow;
-      if (row)
+      if (row) {
         this.selectAlertsOfType(row.alertType);
+      }
     }.bind(this));
 
     return table;
@@ -135,8 +137,7 @@ Polymer({
 
   updateContents_: function() {
     Polymer.dom(this.$.result_area).textContent = '';
-    if (this.model_ === undefined)
-      return;
+    if (this.model_ === undefined) return;
 
     var panel = this.createAlertsTable_(this.model_.alerts);
     Polymer.dom(this.$.result_area).appendChild(panel);