Refactor LoopHandler to avoid calling KernelAstAdapter.getNode

pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart

 // Copyright (c) 2016, 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.
 
 import 'package:js_runtime/shared/embedded_names.dart';
 import 'package:kernel/ast.dart' as ir;
 
 import '../closure.dart';
 import '../common.dart';
 import '../compiler.dart';
@@ skipping 304 matching lines @@
     MemberEntity constructorBody =
         ConstructorBodyElementX.createFromResolvedAst(element.resolvedAst);
     assert(constructorBody != null);
     return constructorBody;
   }
 
   @override
   Spannable getSpannable(MemberEntity member, ir.Node node) {
     return getNode(node);
   }
+
+  @override
+  LoopClosureRepresentationInfo getClosureRepresentationInfoForLoop(
+      ClosureClassMaps closureClassMaps, ir.TreeNode node) {
+    return closureClassMaps.getClosureRepresentationInfoForLoop(getNode(node));
+  }
 }
 
 /// Visitor that converts kernel dart types into [ResolutionDartType].
 class DartTypeConverter extends ir.DartTypeVisitor<ResolutionDartType> {
   final KernelAstAdapter astAdapter;
   bool topLevel = true;
 
   DartTypeConverter(this.astAdapter);
 
   ResolutionDartType convert(ir.DartType type) {
@@ skipping 300 matching lines @@
   TypeMask selectorTypeOf(Selector selector, TypeMask mask) {
     return TypeMaskFactory.inferredTypeForSelector(
         selector, mask, _globalInferenceResults);
   }
 
   TypeMask typeFromNativeBehavior(
       native.NativeBehavior nativeBehavior, ClosedWorld closedWorld) {
     return TypeMaskFactory.fromNativeBehavior(nativeBehavior, closedWorld);
   }
 }