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

pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart

 // Copyright (c) 2013, 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 dart2js.ir_builder_task;
 
 import '../closure.dart' as closurelib;
 import '../closure.dart' hide ClosureScope;
 import '../constants/expressions.dart';
 import '../dart_types.dart';
@@ skipping 400 matching lines @@
   }
 
   visitWhile(ast.While node) {
     irBuilder.buildWhile(
         buildCondition: subbuild(node.condition),
         buildBody: subbuild(node.body),
         target: elements.getTargetDefinition(node),
         closureScope: getClosureScopeForNode(node));
   }
 
-  visitForIn(ast.ForIn node) {
+  visitAsyncForIn(ast.AsyncForIn node) {
+    // await for is not yet implemented.
+    return giveup(node, 'await for');
+  }
+
+  visitSyncForIn(ast.SyncForIn node) {
     // [node.declaredIdentifier] can be either an [ast.VariableDefinitions]
     // (defining a new local variable) or a send designating some existing
     // variable.
     ast.Node identifier = node.declaredIdentifier;
     ast.VariableDefinitions variableDeclaration =
         identifier.asVariableDefinitions();
     Element variableElement = elements.getForInVariable(node);
     Selector selector = elements.getSelector(identifier);
 
     irBuilder.buildForIn(
@@ skipping 2297 matching lines @@
   SourceInformation buildCall(ast.Node node) {
     return new PositionSourceInformation(
         new TokenSourceLocation(sourceFile, node.getBeginToken(), name));
   }
 
   @override
   SourceInformationBuilder forContext(AstElement element) {
     return new PositionSourceInformationBuilder(element);
   }
 }