Convert the inspector framework to use ES6 classes.

sky/framework/inspector/indexeddb-agent.sky

 <script>
-function IndexedDB() {
+class IndexedDB {
+  // Needed to make the inspector not throw an exception.
+  requestDatabaseNames() {
+    return { "databaseNames": [] };
+  }
 }
 
-// Needed to make the inspector not throw an exception.
-IndexedDB.prototype.requestDatabaseNames = function() {
-  return { "databaseNames": [] };
-};
-
 module.exports = IndexedDB;
 </script>