Revert "Model 'await for' as an explicit node in tree and fix its handling."

pkg/compiler/lib/src/typechecker.dart

Index: pkg/compiler/lib/src/typechecker.dart
diff --git a/pkg/compiler/lib/src/typechecker.dart b/pkg/compiler/lib/src/typechecker.dart
index 078086c823def58beca12c5ff43afed21d522686..04a7a432fff6f91592c8d1c2062b1670e7b292dc 100644
--- a/pkg/compiler/lib/src/typechecker.dart
+++ b/pkg/compiler/lib/src/typechecker.dart
@@ -1719,13 +1719,7 @@ class TypeCheckerVisitor extends Visitor<DartType> {
     return const StatementType();
   }
 
-  visitAsyncForIn(AsyncForIn node) {
-    analyze(node.expression);
-    analyze(node.body);
-    return const StatementType();
-  }
-
-  visitSyncForIn(SyncForIn node) {
+  visitForIn(ForIn node) {
     analyze(node.expression);
     analyze(node.body);
     return const StatementType();