chore(build): Add WebWorker bundle.

Closes #3207

Closes #3881

modules/angular2/src/core/facade/lang.ts

@@ -1,5 +1,23 @@
 /// <reference path="../../../globals.d.ts" />
-var _global: BrowserNodeGlobal = <any>(typeof window === 'undefined' ? global : window);
+
+// TODO(jteplitz602): Load WorkerGlobalScope from lib.webworker.d.ts file #3492
+declare var WorkerGlobalScope;
+var globalScope: BrowserNodeGlobal;
+if (typeof window === 'undefined') {
+  if (typeof WorkerGlobalScope !== 'undefined' && self instanceof WorkerGlobalScope) {
+    // TODO: Replace any with WorkerGlobalScope from lib.webworker.d.ts #3492
+    globalScope = <any>self;
+  } else {
+    globalScope = <any>global;
+  }
+} else {
+  globalScope = <any>window;
+};
+
+// Need to declare a new variable for global here since TypeScript
+// exports the original value of the symbol.
+var _global: BrowserNodeGlobal = globalScope;
+
 export {_global as global};
 
 export var Type = Function;

modules/angular2/src/web_workers/shared/message_bus.ts

@@ -1,5 +1,6 @@
 import {EventEmitter} from 'angular2/src/core/facade/async';
 import {BaseException} from 'angular2/src/core/facade/lang';
+export {EventEmitter, Observable} from 'angular2/src/core/facade/async';
 
 function _abstract() {
   throw new BaseException("This method is abstract");

modules/angular2/src/web_workers/ui/application.ts

@@ -6,6 +6,7 @@ import {
 import {MessageBus} from 'angular2/src/web_workers/shared/message_bus';
 import {BaseException} from "angular2/src/core/facade/lang";
 import {bootstrapUICommon} from "angular2/src/web_workers/ui/impl";
+export * from 'angular2/src/web_workers/shared/message_bus';
 
 /**
  * Bootstrapping a WebWorker

modules/angular2/src/web_workers/worker/application.ts

@@ -10,6 +10,7 @@ import {Promise} from 'angular2/src/core/facade/async';
 import {bootstrapWebWorkerCommon} from "angular2/src/web_workers/worker/application_common";
 import {ApplicationRef} from "angular2/src/core/application_ref";
 import {Injectable} from "angular2/di";
+export * from "angular2/src/web_workers/shared/message_bus";
 
 // TODO(jteplitz602) remove this and compile with lib.webworker.d.ts (#3492)
 interface PostMessageInterface {