Support new malformed types semantics.

sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
index 7b04eb263069a66474061172b41107af8e18598b..28f10dd44ba62f456303ebb5e84a87abdc5410ea 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -184,12 +184,10 @@ class CodeEmitterTask extends CompilerTask {
     checkedClasses = new Set<ClassElement>();
     checkedFunctionTypes = new Set<FunctionType>();
     compiler.codegenWorld.isChecks.forEach((DartType t) {
-      if (!t.isMalformed) {
-        if (t is InterfaceType) {
-          checkedClasses.add(t.element);
-        } else if (t is FunctionType) {
-          checkedFunctionTypes.add(t);
-        }
+      if (t is InterfaceType) {
+        checkedClasses.add(t.element);
+      } else if (t is FunctionType) {
+        checkedFunctionTypes.add(t);
       }
     });
   }
@@ -1547,8 +1545,8 @@ class CodeEmitterTask extends CompilerTask {
   bool canGenerateCheckedSetter(Element member) {
     DartType type = member.computeType(compiler).unalias(compiler);
     if (type.element.isTypeVariable() ||
-        (type is FunctionType && type.containsTypeVariables) || 
-        type.element == compiler.dynamicClass ||
+        (type is FunctionType && type.containsTypeVariables) ||
+        type.treatAsDynamic ||
         type.element == compiler.objectClass) {
       // TODO(ngeoffray): Support type checks on type parameters.
       return false;