Copy all fields of NullCheck

pkg/compiler/lib/src/js_backend/codegen/codegen.dart

 // Copyright (c) 2014, 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 code_generator;
 
 import 'glue.dart';
 
 import '../../closure.dart' show
     ClosureClassElement;
@@ skipping 1003 matching lines @@
   @override
   void visitYield(tree_ir.Yield node) {
     js.Expression value = visitExpression(node.input);
     accumulator.add(new js.DartYield(value, node.hasStar));
     visitStatement(node.next);
   }
 
   @override
   void visitNullCheck(tree_ir.NullCheck node) {
     js.Expression value = visitExpression(node.value);
-    js.Expression access = node.selector != null
+    // TODO(sra): Try to use the selector even when [useSelector] is false. The
+    // reason we use 'toString' is that it is always defined so avoids a slow
+    // lookup (in V8) of an absent property. We could use the property for the
+    // selector if we knew it was present. The property is present if the
+    // associated method was not inlined away, or if there is a noSuchMethod
+    // hook for that selector. We don't know these things here, but the decision
+    // could be deferred by creating a deferred property that was resolved after
+    // codegen.
+    js.Expression access = node.selector != null && node.useSelector
         ? js.js('#.#', [value, glue.invocationName(node.selector)])
         : js.js('#.toString', [value]);
     if (node.condition != null) {
       js.Expression condition = visitExpression(node.condition);
       js.Statement body = isNullReturn(node.next)
           ? new js.ExpressionStatement(access)
           : new js.Return(access);
       accumulator.add(new js.If.noElse(condition, body));
     } else {
       accumulator.add(new js.ExpressionStatement(access));
@@ skipping 179 matching lines @@
   void registerDefaultParameterValues(ExecutableElement element) {
     if (element is! FunctionElement) return;
     FunctionElement function = element;
     if (function.isStatic) return; // Defaults are inlined at call sites.
     function.functionSignature.forEachOptionalParameter((param) {
       ConstantValue constant = glue.getDefaultParameterValue(param);
       registry.registerCompileTimeConstant(constant);
     });
   }
 }