Pass in `this` as a free variable to the closure class

pkg/compiler/lib/src/kernel/element_map_impl.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.
 
 library dart2js.kernel.element_map;
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../closure.dart' show BoxLocal, ThisLocal;
 import '../common.dart';
@@ skipping 2281 matching lines @@
         closureEntity,
         thisLocal);
     int fieldNumber = 0;
     for (ir.VariableDeclaration variable in info.freeVariables) {
       // Make a corresponding field entity in this closure class for every
       // single freeVariable in the KernelScopeInfo.freeVariable.
       _constructClosureField(
           member,
           cls,
           memberMap,
+          localsMap.getLocalVariable(variable),
           variable,
+          variable.isConst,
+          !(variable.isFinal || variable.isConst),
           boxedCapturedVariables,
           fieldNumber,
           info.capturedVariablesAccessor,
+          localsMap);
+      fieldNumber++;
+    }
+    if (info.thisUsedAsFreeVariable) {
+      _constructClosureField(
+          member,
+          cls,
+          memberMap,
+          cls.thisLocal,
+          getMemberDefinition(member).node,
+          true,
+          false,
+          boxedCapturedVariables,
+          fieldNumber,
+          info.capturedVariablesAccessor,
           localsMap);
       fieldNumber++;
     }
 
     FunctionEntity callMethod = cls.callMethod = new JClosureCallMethod(
         _memberData.length,
         cls,
         _getParameterStructure(node),
         _getAsyncMarker(node));
     _memberList.add(cls.callMethod);
 
     _memberData.add(new ClosureFunctionData(
         new ClosureMemberDefinition(callMethod, closureData.definition.location,
             MemberKind.closureCall, node.parent),
         getFunctionType(node),
         node));
     memberMap[cls.callMethod.name] = cls.callMethod;
     return cls;
   }
 
   _constructClosureField(
       MemberEntity member,
       KernelClosureClass cls,
       Map<String, MemberEntity> memberMap,
-      ir.VariableDeclaration variable,
+      Local capturedLocal,
+      ir.TreeNode sourceNode,
+      bool isConst,
+      bool isAssignable,
       Map<Local, JRecordField> boxedCapturedVariables,
       int fieldNumber,
       NodeBox box,
       KernelToLocalsMap localsMap) {
-    // NOTE: This construction order may be slightly different than the
+    // NOTE: This construction *order* may be slightly different than the
     // old Element version. The old version did all the boxed items and then
     // all the others.
-    Local capturedLocal = localsMap.getLocalVariable(variable);
     JRecordField field = boxedCapturedVariables[capturedLocal];
     FieldEntity closureField = new JClosureField(
         _getClosureVariableName(capturedLocal.name, fieldNumber),
         _memberData.length,
         cls,
-        variable.isConst,
-        variable.isFinal || variable.isConst);
+        isConst,
+        isAssignable);
     _memberList.add(closureField);
     _memberData.add(new ClosureFieldData(new ClosureMemberDefinition(
         cls.localToFieldMap[capturedLocal],
-        computeSourceSpanFromTreeNode(variable),
+        computeSourceSpanFromTreeNode(sourceNode),
         MemberKind.closureField,
-        variable)));
+        sourceNode)));
     memberMap[closureField.name] = closureField;
     if (boxedCapturedVariables.containsKey(capturedLocal)) {
       cls.localToFieldMap[field.box] = closureField;
       cls.boxedVariables[capturedLocal] = field;
     } else {
       cls.localToFieldMap[capturedLocal] = closureField;
     }
   }
 
   // Returns a non-unique name for the given closure element.
@@ skipping 44 matching lines @@
   ///
   /// These names are not used in generated code, just as element name.
   String _getClosureVariableName(String name, int id) {
     return "_captured_${name}_$id";
   }
 
   String getDeferredUri(ir.LibraryDependency node) {
     throw new UnimplementedError('JsKernelToElementMap.getDeferredUri');
   }
 }