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

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 0d9a9df1764227379ffeda3a30605821a994d4bf..61cc575f151c06307dee6954abcabd24fc2e6ba7 100644
--- a/pkg/compiler/lib/src/js_model/closure.dart
+++ b/pkg/compiler/lib/src/js_model/closure.dart
@@ -293,8 +293,15 @@ class JsScopeInfo extends ScopeInfo {
             info.hasThisLocal ? new ThisLocal(localsMap.currentMember) : null,
         this.localsUsedInTryOrSync =
             info.localsUsedInTryOrSync.map(localsMap.getLocalVariable).toSet(),
-        this.freeVariables =
-            info.freeVariables.map(localsMap.getLocalVariable).toSet();
+        this.freeVariables = new Set<Local>() {
+    for (var variable in info.freeVariables) {
+      if (variable is ThisVariable) {
+        freeVariables.add(thisLocal);
+      } else {
+        freeVariables.add(localsMap.getLocalVariable(variable));
+      }
+    }
+  }
 
   void forEachBoxedVariable(f(Local local, FieldEntity field)) {
     boxedVariables.forEach((Local l, JRecordField box) {