Lookup getClosureScope by member instead of node

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

Index: pkg/compiler/lib/src/js_model/closure.dart
diff --git a/pkg/compiler/lib/src/js_model/closure.dart b/pkg/compiler/lib/src/js_model/closure.dart
index 01aa7ac13fb82e04a7b6f3d71c673925d199718a..7202e5ce7e733a36b12efa70d8e26e8b12da4c4e 100644
--- a/pkg/compiler/lib/src/js_model/closure.dart
+++ b/pkg/compiler/lib/src/js_model/closure.dart
@@ -126,13 +126,17 @@ class KernelClosureConversionTask extends ClosureConversionTask<ir.Node> {
     return getClosureRepresentationInfo(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) =>
+  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.
   LoopClosureScope getLoopClosureScope(ir.Node loopNode) =>