fix(ddc): router, compiler, web worker fixes for DDC

Also enable DDC checks across all non-web worker playground apps. We are
now down to 2 DDC errors across all of them. The remaining two need to be
fixed in package:analyzer, not in angular.

BREAKING CHANGE:

- there's a chance of breakage as router's Instruction constructor
  signature changed.

Closes #6693

modules/angular2/src/compiler/template_normalizer.ts

@@ -112,6 +112,10 @@ class TemplatePreparseVisitor implements HtmlAstVisitor {
       case PreparsedElementType.STYLESHEET:
         this.styleUrls.push(preparsedElement.hrefAttr);
         break;
+      default:
+        // DDC reports this as error. See:
+        // https://github.com/dart-lang/dev_compiler/issues/428
+        break;
     }
     if (preparsedElement.nonBindable) {
       this.ngNonBindableStackCount++;