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

tracing/tracing/ui/base/checkbox.html

Index: tracing/tracing/ui/base/checkbox.html
diff --git a/tracing/tracing/ui/base/checkbox.html b/tracing/tracing/ui/base/checkbox.html
index 5862aa17d79b3d017dd19c13b186b6611ee56ff4..9d47136f4ac6154b6e9bc4ed72cc0daa169c6005 100644
--- a/tracing/tracing/ui/base/checkbox.html
+++ b/tracing/tracing/ui/base/checkbox.html
@@ -44,8 +44,7 @@ found in the LICENSE file.
     },
 
     maybeUpdateElements_: function() {
-      if (!this.is_ready_)
-        return;
+      if (!this.is_ready_) return;
       this.$.label.innerText = this.label_;
       this.$.checkbox.checked = this.checked_;
     },
@@ -55,8 +54,9 @@ found in the LICENSE file.
     },
 
     set defaultCheckedValue(defaultCheckedValue) {
-      if (!this.needsInit_)
+      if (!this.needsInit_) {
         throw new Error('Already initialized.');
+      }
       this.defaultCheckedValue_ = defaultCheckedValue;
       this.maybeInit_();
     },
@@ -66,19 +66,17 @@ found in the LICENSE file.
     },
 
     set settingsKey(settingsKey) {
-      if (!this.needsInit_)
+      if (!this.needsInit_) {
         throw new Error('Already initialized.');
+      }
       this.settingsKey_ = settingsKey;
       this.maybeInit_();
     },
 
     maybeInit_: function() {
-      if (!this.needsInit_)
-        return;
-      if (this.settingsKey_ === undefined)
-        return;
-      if (this.defaultCheckedValue_ === undefined)
-        return;
+      if (!this.needsInit_) return;
+      if (this.settingsKey_ === undefined) return;
+      if (this.defaultCheckedValue_ === undefined) return;
       this.needsInit_ = false;
       this.checked = tr.b.Settings.get(
           this.settingsKey_, this.defaultCheckedValue_);