cps2js: Fix translation of captured 'this'.

pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart

 // Copyright (c) 2013, 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.ir_builder;
 
 import '../constants/expressions.dart';
 import '../constants/values.dart' show PrimitiveConstantValue;
 import '../dart_types.dart';
 import '../dart2jslib.dart';
@@ skipping 1804 matching lines @@
   /// Add [functionElement] to the environment with provided [definition].
   void declareLocalFunction(LocalFunctionElement functionElement,
                             ClosureClassElement classElement) {
     ir.Primitive closure = buildFunctionExpression(classElement);
     declareLocalVariable(functionElement, initialValue: closure);
   }
 
   ir.Primitive buildFunctionExpression(ClosureClassElement classElement) {
     List<ir.Primitive> arguments = <ir.Primitive>[];
     for (ClosureFieldElement field in classElement.closureFields) {
-      arguments.add(environment.lookup(field.local));
+      // Captured 'this' is not available as a local in the current environment,
+      // so treat that specially.
+      ir.Primitive value = field.local is ThisLocal
+          ? buildThis()
+          : environment.lookup(field.local);
+      arguments.add(value);
     }
     ir.Primitive closure = new ir.CreateInstance(classElement, arguments);
     add(new ir.LetPrim(closure));
     return closure;
   }
 
   /// Create a read access of [local].
   ir.Primitive buildLocalGet(LocalElement local) {
     assert(isOpen);
     ClosureLocation location = jsState.boxedVariables[local];
@@ skipping 171 matching lines @@
   ClosureEnvironment(this.selfReference, this.thisLocal, this.freeVariables);
 }
 
 /// Information about which variables are captured by a nested function.
 ///
 /// This is used by the [DartIrBuilder] instead of [ClosureScope] and
 /// [ClosureEnvironment].
 abstract class DartCapturedVariableInfo {
   Iterable<Local> get capturedVariables;
 }