Expose WorkerGlobalScope interface in worker environment

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

-if (this.importScripts)
+if (self.importScripts) {
     importScripts('../../fast/js/resources/js-test-pre.js');
 
+    if (!self.postMessage) {
+        // Shared worker.  Make postMessage send to the newest client, which in
+        // our tests is the only client.
+
+        // Store messages for sending until we have somewhere to send them.
+        self.postMessage = function(message) {
+            if (typeof self.pendingMessages === "undefined")
+                self.pendingMessages = [];
+            self.pendingMessages.push(message);
+        };
+        self.onconnect = function(event) {
+            self.postMessage = function(message) {
+                event.ports[0].postMessage(message);
+            };
+            // Offload any stored messages now that someone has connected to us.
+            if (typeof self.pendingMessages === "undefined")
+                return;
+            while (self.pendingMessages.length)
+                event.ports[0].postMessage(self.pendingMessages.shift());
+        };
+    }
+}
+
 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();