Resolve type Dynamic and implement black listing.

dart/frog/leg/lib/js_helper.dart

Index: dart/frog/leg/lib/js_helper.dart
diff --git a/dart/frog/leg/lib/js_helper.dart b/dart/frog/leg/lib/js_helper.dart
index 98361a25db9ac4d83c7ba8ae57aa50d5375ec944..08eaa6224ba32b3c99aba60351229816c590c3a0 100644
--- a/dart/frog/leg/lib/js_helper.dart
+++ b/dart/frog/leg/lib/js_helper.dart
@@ -1399,3 +1399,18 @@ jsPropertyAccess(var jsObject, String property) {
  * FallThroughError exception that will be thrown.
  */
 getFallThroughError() => const FallThroughError();
+
+/**
+ * Represents the type Dynamic. The compiler treats this specially.
+ */
+interface Dynamic {
+}
+
+/**
+ * Represents the type of Null. The compiler treats this specially.
+ */
+class Null {
+  factory Null() {
+    throw UnsupportedOperationException('new Null()');
+  }
+}