Fix another closure/type variable error by using analyzeTypeVariables.

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 537 matching lines @@
                && !compiler.enableUserAssertions) {
       return;
     }
     node.visitChildren(this);
   }
 
   visitSendSet(SendSet node) {
     Element element = elements[node];
     if (Elements.isLocal(element)) {
       mutatedVariables.add(element);
-    }
-    if (Elements.isLocal(element) &&
-        element.computeType(compiler).containsTypeVariables) {
-      registerNeedsThis();
+      if (compiler.enableTypeAssertions) {
+        analyzeTypeVariables(element.computeType(compiler));
+      }
     }
     super.visitSendSet(node);
   }
 
   visitNewExpression(NewExpression node) {
     DartType type = elements.getType(node);
     analyzeType(type);
     node.visitChildren(this);
   }
 
@@ skipping 256 matching lines @@
   }
 
   visitTryStatement(TryStatement node) {
     // TODO(ngeoffray): implement finer grain state.
     bool oldInTryStatement = inTryStatement;
     inTryStatement = true;
     node.visitChildren(this);
     inTryStatement = oldInTryStatement;
   }
 }