Support user generated custom native JS classes.

pkg/compiler/lib/src/types/types.dart

 // Copyright (c) 2012, 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.
 
 library types;
 
 import '../common.dart';
 import '../common/backend_api.dart' show
     Backend;
 import '../common/tasks.dart' show
@@ skipping 268 matching lines @@
       typesInferrer.analyzeMain(mainElement);
     });
     typesInferrer.clear();
   }
 
   /**
    * Return the (inferred) guaranteed type of [element] or null.
    */
   TypeMask getGuaranteedTypeOfElement(Element element) {
     return measure(() {
+      // TODO(24489): trust some JsInterop types.
+      if (element.isJsInterop) {
+        return dynamicType;
+      }
       TypeMask guaranteedType = typesInferrer.getTypeOfElement(element);
       return guaranteedType;
     });
   }
 
   TypeMask getGuaranteedReturnTypeOfElement(Element element) {
     return measure(() {
+      // TODO(24489): trust some JsInterop types.
+      if (element.isJsInterop) {
+        return dynamicType;
+      }
+
       TypeMask guaranteedType =
           typesInferrer.getReturnTypeOfElement(element);
       return guaranteedType;
     });
   }
 
   /**
    * Return the (inferred) guaranteed type of [node] or null.
    * [node] must be an AST node of [owner].
    */
   TypeMask getGuaranteedTypeOfNode(owner, node) {
     return measure(() {
       TypeMask guaranteedType = typesInferrer.getTypeOfNode(owner, node);
       return guaranteedType;
     });
   }
 
   /**
    * Return the (inferred) guaranteed type of [selector] or null.
    */
   TypeMask getGuaranteedTypeOfSelector(Selector selector, TypeMask mask) {
     return measure(() {
       TypeMask guaranteedType =
           typesInferrer.getTypeOfSelector(selector, mask);
       return guaranteedType;
     });
   }
 }