refactor(compiler): don’t rely on external css parser

We used to use different external css parsers,
depending on the `DomAdapter`. This lead to
inconsistent behavior and environment specific errors.

Closes #5006
Closes #4993

modules/angular2/test/web_workers/debug_tools/bootstrap.server.spec.dart

@@ -1,5 +1,6 @@
 library angular2.test.web_workers.debug_tools.bootstrap;
 
+import 'package:angular2/src/core/dom/html_adapter.dart';
 import "package:angular2/testing_internal.dart";
 import "package:angular2/src/core/reflection/reflection_capabilities.dart";
 import "package:angular2/src/core/reflection/reflection.dart";
@@ -9,6 +10,9 @@ import "../shared/web_worker_test_util.dart";
 import "dart:convert";
 
 main() {
+  Html5LibDomAdapter.makeCurrent();
+  testSetup();
+
   describe("bootstrapWebWorkerCommon", () {
     it("should bootstrap on a Dart VM", () {
       reflector.reflectionCapabilities = new ReflectionCapabilities();