Convert the inspector framework to use ES6 classes.

sky/framework/inspector/worker-agent.sky

Index: sky/framework/inspector/worker-agent.sky
diff --git a/sky/framework/inspector/worker-agent.sky b/sky/framework/inspector/worker-agent.sky
index 580b6b3d751a72a151197800e0c656521fb5d9e3..92201c0f27656def321861cd77fe3be831d20b12 100644
--- a/sky/framework/inspector/worker-agent.sky
+++ b/sky/framework/inspector/worker-agent.sky
@@ -1,12 +1,15 @@
 <script>
-function WorkerAgent() {
-}
+class WorkerAgent {
+  constructor() {
+    Object.preventExtensions(this);
+  }
 
-WorkerAgent.prototype.canInspectWorkers = function() {
-  return {
-    result: false
-  };
-};
+  canInspectWorkers() {
+    return {
+      result: false
+    };
+  }
+}
 
 module.exports = WorkerAgent;
 </script>