Sprinkle some types on the SDK like the static typing fairy.

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/rtti.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// This library defines the association between runtime objects and
 /// runtime types.
 part of dart._runtime;
 
 /// Runtime type information.  This module defines the mapping from
 /// runtime objects to their runtime type information.  See the types
@@ skipping 165 matching lines @@
 lazyAnonymousJSType(name) {
   if (JS('bool', '#.has(#)', _lazyJSTypes, name)) {
     return JS('', '#.get(#)', _lazyJSTypes, name);
   }
   var ret = JS('', 'new #(null, #)', LazyJSType, name);
   JS('', '#.set(#, #)', _lazyJSTypes, name, ret);
   return ret;
 }
 
 /// Given a WrappedType, return the internal runtime type object.
-unwrapType(obj) => obj._wrappedType;
+unwrapType(WrappedType obj) => obj._wrappedType;
 
 _getRuntimeType(value) => JS('', '#[#]', value, _runtimeType);
 getIsNamedConstructor(value) => JS('', '#[#]', value, isNamedConstructor);
 // TODO(bmilligan): Define the symbol in rtti.dart instead of dart_library.js
 // and get rid of the call to dart_library in the JS here.
 getDartLibraryName(value) => JS('', '#[dart_library.dartLibraryName]', value);
 
 /// Tag the runtime type of [value] to be type [t].
 void tag(value, t) {
   JS('', '#[#] = #', value, _runtimeType, t);
 }
 
 void tagComputed(value, compute) {
   JS('', '#(#, #, { get: # })', defineProperty, value, _runtimeType, compute);
 }
 
 void tagLazy(value, compute) {
   JS('', '#(#, #, { get: # })', defineLazyProperty, value, _runtimeType,
       compute);
 }