Type-related fixes

pkg/dev_compiler/lib/js/legacy/dart_sdk.js

Index: pkg/dev_compiler/lib/js/legacy/dart_sdk.js
diff --git a/pkg/dev_compiler/lib/js/legacy/dart_sdk.js b/pkg/dev_compiler/lib/js/legacy/dart_sdk.js
index ab2cabdc5a650612a5bea874c349cb03dd4b1129..8bc7bd061f6c32246a2cc5270b3bbb8099479d08 100644
--- a/pkg/dev_compiler/lib/js/legacy/dart_sdk.js
+++ b/pkg/dev_compiler/lib/js/legacy/dart_sdk.js
@@ -1914,7 +1914,8 @@ dart_library.library('dart_sdk', null, /* Imports */[
     if (result != null) return dart.wrapType(result);
     let extension = dart.getExtensionType(obj);
     if (extension != null) {
-      return obj[dartx.runtimeType];
+      result = obj[dartx.runtimeType];
+      return result != null ? result : dart.wrapType(extension);
     }
     if (typeof obj == "function") {
       return dart.wrapType(dart.getReifiedType(obj));
@@ -13200,6 +13201,10 @@ dart_library.library('dart_sdk', null, /* Imports */[
     return _js_mirrors._dart.wrapType(obj);
   };
   dart.fn(_js_mirrors._wrap, dynamicTodynamic$());
+  _js_mirrors._runtimeType = function(obj) {
+    return _js_mirrors._wrap(_js_mirrors._dart.getReifiedType(obj));
+  };
+  dart.fn(_js_mirrors._runtimeType, dynamicTodynamic$());
   _js_mirrors._unimplemented = function(t, i) {
     dart.throw(new core.UnimplementedError(dart.str`${t}.${_js_mirrors.getName(i.memberName)} unimplemented`));
   };
@@ -13312,7 +13317,7 @@ dart_library.library('dart_sdk', null, /* Imports */[
     }
     get type() {
       if (this.reflectee == null) return mirrors.reflectClass(dart.wrapType(core.Null));
-      return mirrors.ClassMirror._check(_js_mirrors.reflectType(core.Type._check(dart.runtimeType(this.reflectee))));
+      return mirrors.ClassMirror._check(_js_mirrors.reflectType(core.Type._check(_js_mirrors._runtimeType(this.reflectee))));
     }
     _(reflectee) {
       this.reflectee = reflectee;