Lookup getClosureScope by member instead of node

pkg/compiler/lib/src/js_model/closure.dart

 // Copyright (c) 2017, 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/tasks.dart';
 import '../elements/entities.dart';
 import '../kernel/element_map.dart';
@@ skipping 108 matching lines @@
     assert(entity != null);
 
     _closureRepresentationMap[entity] = closureClass;
   }
 
   @override
   ScopeInfo getScopeInfo(Entity entity) {
     return getClosureRepresentationInfo(entity);
   }
 
+  // TODO(efortuna): Eventually closureScopeMap[node] should always be non-null,
+  // and we should just test that with an assert.
+  ClosureScope _getClosureScope(ir.Node node) =>
+      _closureScopeMap[node] ?? const ClosureScope();
+
+  @override
+  ClosureScope getClosureScope(MemberEntity entity) {
+    return _getClosureScope(_elementMap.getMemberNode(entity));
+  }
+
   @override
   // TODO(efortuna): Eventually closureScopeMap[node] should always be non-null,
   // and we should just test that with an assert.
-  ClosureScope getClosureScope(ir.Node node) =>
-      _closureScopeMap[node] ?? const ClosureScope();
-
-  @override
-  // TODO(efortuna): Eventually closureScopeMap[node] should always be non-null,
-  // and we should just test that with an assert.
   LoopClosureScope getLoopClosureScope(ir.Node loopNode) =>
       _closureScopeMap[loopNode] ?? const LoopClosureScope();
 
   @override
   // TODO(efortuna): Eventually closureRepresentationMap[node] should always be
   // non-null, and we should just test that with an assert.
   ClosureRepresentationInfo getClosureRepresentationInfo(Entity entity) =>
       _closureRepresentationMap[entity] ?? const ClosureRepresentationInfo();
 }
 
@@ skipping 91 matching lines @@
   // TODO(efortuna): Implement.
   bool isVariableBoxed(Local variable) => false;
 
   // TODO(efortuna): Implement.
   // Why is this closure not actually a closure? Well, to properly call
   // ourselves a closure, we need to register the new closure class with the
   // ClosedWorldRefiner, which currently only takes elements. The change to
   // that (and the subsequent adjustment here) will follow soon.
   bool get isClosure => false;
 }