Add webexposed/ layout test that documents all the global constructors in the Worker context

LayoutTests/webexposed/resources/global-context-constructors-listing.js

+if (this.importScripts)
+    importScripts('../../fast/js/resources/js-test-pre.js');
+
+function isConstructor(propertyName) {
+    var descriptor = Object.getOwnPropertyDescriptor(this, propertyName);
+    if (descriptor.value == undefined || descriptor.value.prototype == undefined)
+        return false;
+    return descriptor.writable && !descriptor.enumerable && descriptor.configurable;
+}
+
+var constructorNames = [];
+var propertyNames = Object.getOwnPropertyNames(this);
+for (var i = 0; i < propertyNames.length; i++) {
+    if (isConstructor(propertyNames[i]))
+        constructorNames[constructorNames.length] = propertyNames[i];
+}
+
+
+constructorNames.sort();
+for (var i = 0; i < constructorNames.length; i++)
+    debug(constructorNames[i]);
+
+if (isWorker())
+  finishJSTest();