fix #27631, get/set methods no longer shadow index operator

pkg/dev_compiler/lib/src/compiler/code_generator.dart

Index: pkg/dev_compiler/lib/src/compiler/code_generator.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/code_generator.dart b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
index d2d952ffb633ae2afb31e3ec59f7de8ddb92b826..cdfc7e56cea8e71302678604a9a154ad2310265b 100644
--- a/pkg/dev_compiler/lib/src/compiler/code_generator.dart
+++ b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
@@ -1488,6 +1488,9 @@ class CodeGenerator extends GeneralizingAstVisitor
     result.add(new JS.Method(name, getter, isGetter: true));
 
     if (field.isFinal) {
+      // TODO(jmesserly): vsm@ commented that this seems unnecessary if we
+      // don't have a super setter. I'm not sure either why this code was
+      // introduced.
       var setter = js.call('function(value) { super[#] = value; }', [name]);
       result.add(new JS.Method(name, setter, isSetter: true));
     } else {