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

pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart

Index: pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart
diff --git a/pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart b/pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart
index b15a4e2fbb014e8263d92f0ac9b8ec6cf99545fc..8e29ca084fa44701f2e3f2a3c9890ffbf31b395b 100644
--- a/pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart
+++ b/pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.dart
@@ -775,10 +775,11 @@ class TreePrinter {
       } else {
         left = makeVariableDeclarations(stmt.leftHandValue);
       }
-      return new tree.SyncForIn(
+      return new tree.ForIn(
           left,
           makeExpression(stmt.expression),
           makeStatement(stmt.body, shortIf: shortIf),
+          awaitToken,
           forToken,
           inToken);
     } else if (stmt is FunctionDeclaration) {