refactor(dart/transform tests): Use actual directive def'n instead of mock.

In the transformer unit tests, we previously used a mock directive annotation. This update
substitutes the actual Angular2 directive annotations.

Closes #706

modules/angular2/src/transform/codegen.dart

@@ -224,6 +224,14 @@ abstract class _TransformVisitor extends ToSourceVisitor {
     }
   }
 
+  @override
+  Object visitPrefixedIdentifier(PrefixedIdentifier node) {
+    // We add our own prefixes in [visitSimpleIdentifier], discard any used in
+    // the original source.
+    _visitNode(node.identifier);
+    return null;
+  }
+
   @override
   Object visitSimpleIdentifier(SimpleIdentifier node) {
     // Make sure the identifier is prefixed if necessary.
@@ -281,6 +289,7 @@ class _CtorTransformVisitor extends _TransformVisitor {
   @override
   Object visitDefaultFormalParameter(DefaultFormalParameter node) {
     _visitNode(node.parameter);
+    // Ignore the declared default value.
     return null;
   }