Make `this` available in closures if a type variable is used as expression.

sdk/lib/_internal/compiler/implementation/closure.dart

 // Copyright (c) 2012, 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 closureToClassMapper;
 
 import "elements/elements.dart";
 import "dart2jslib.dart";
 import "dart_types.dart";
 import "scanner/scannerlib.dart" show Token;
@@ skipping 387 matching lines @@
         }
       } else {
         visit(definition);
       }
     }
   }
 
   visitIdentifier(Identifier node) {
     if (node.isThis()) {
       useLocal(closureData.thisElement);
+    } else {
+      Element element = elements[node];
+      if (element != null && element.kind == ElementKind.TYPE_VARIABLE) {
+        useLocal(closureData.thisElement);
+      }
     }
     node.visitChildren(this);
   }
 
   visitSend(Send node) {
     Element element = elements[node];
     if (Elements.isLocal(element)) {
       useLocal(element);
     } else if (node.receiver == null &&
                Elements.isInstanceSend(node, elements)) {
@@ skipping 278 matching lines @@
   }
 
   visitTryStatement(TryStatement node) {
     // TODO(ngeoffray): implement finer grain state.
     bool oldInTryStatement = inTryStatement;
     inTryStatement = true;
     node.visitChildren(this);
     inTryStatement = oldInTryStatement;
   }
 }