Reduce use of getClosureInfoForMember and cleanup closure_test

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:kernel/ast.dart' as ir;
 
 import '../closure.dart';
 import '../common.dart';
 import '../compiler.dart';
 import '../constants/expressions.dart';
@@ skipping 115 matching lines @@
       originTarget = originTarget.origin;
     }
     if (originTarget is MethodElement) {
       if (originTarget is ConstructorBodyElement) {
         ConstructorBodyElement body = originTarget;
         originTarget = body.constructor;
       }
       target = kernel.functions[originTarget];
       // Closures require a lookup one level deeper in the closure class mapper.
       if (target == null) {
-        MethodElement originTargetFunction = originTarget;
-        ClosureRepresentationInfo classMap = _compiler
-            .backendStrategy.closureDataLookup
-            .getClosureInfoForMember(originTargetFunction);
-        if (classMap.closureEntity != null) {
-          target = kernel.localFunctions[classMap.closureEntity];
-        }
+        SynthesizedCallMethodElementX originTargetFunction = originTarget;
+        target = kernel.localFunctions[originTargetFunction.expression];
       }
     } else if (originTarget is FieldElement) {
       target = kernel.fields[originTarget];
     }
     assert(target != null);
     return target;
   }
 
   MemberDefinition getMemberDefinition(MemberElement member) {
     ir.Node node = getMemberNode(member);
@@ skipping 575 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);
   }
 }