Type-related fixes

pkg/dev_compiler/lib/js/common/dart_sdk.js

Index: pkg/dev_compiler/lib/js/common/dart_sdk.js
diff --git a/pkg/dev_compiler/lib/js/common/dart_sdk.js b/pkg/dev_compiler/lib/js/common/dart_sdk.js
index 259b2e1e569b82c76368e0a605db3f5bf934b734..5070c1bb3044208874c564429ddfb1164421144c 100644
--- a/pkg/dev_compiler/lib/js/common/dart_sdk.js
+++ b/pkg/dev_compiler/lib/js/common/dart_sdk.js
@@ -1913,7 +1913,8 @@
     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));
@@ -13199,6 +13200,10 @@
     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`));
   };
@@ -13311,7 +13316,7 @@
     }
     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;