Move native and js interop properties from the element model to the JS backend

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

Index: pkg/compiler/lib/src/types/types.dart
diff --git a/pkg/compiler/lib/src/types/types.dart b/pkg/compiler/lib/src/types/types.dart
index 9d91f99ff7380b22aa009e8a15427bd78c2c3e1a..733d119f874ec197978646b2cd78667b0d08c08e 100644
--- a/pkg/compiler/lib/src/types/types.dart
+++ b/pkg/compiler/lib/src/types/types.dart
@@ -287,7 +287,7 @@ class TypesTask extends CompilerTask {
   TypeMask getGuaranteedTypeOfElement(Element element) {
     return measure(() {
       // TODO(24489): trust some JsInterop types.
-      if (element.isJsInterop) {
+      if (compiler.backend.isJsInterop(element)) {
         return dynamicType;
       }
       TypeMask guaranteedType = typesInferrer.getTypeOfElement(element);
@@ -298,7 +298,7 @@ class TypesTask extends CompilerTask {
   TypeMask getGuaranteedReturnTypeOfElement(Element element) {
     return measure(() {
       // TODO(24489): trust some JsInterop types.
-      if (element.isJsInterop) {
+      if (compiler.backend.isJsInterop(element)) {
         return dynamicType;
       }