Support enums in dart2js.

pkg/compiler/lib/src/compiler.dart

Index: pkg/compiler/lib/src/compiler.dart
diff --git a/pkg/compiler/lib/src/compiler.dart b/pkg/compiler/lib/src/compiler.dart
index fad4298d35af97a8d80cc6d5b4c10ba27292c562..e1b1932dbd370268eb85b5ee9769edd831351c45 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -721,6 +721,9 @@ abstract class Compiler implements DiagnosticListener {
   /// `true` if async/await features are supported.
   final bool enableAsyncAwait;
 
+  /// `true` if enum declarations are supported.
+  final bool enableEnums;
+
   /// If `true`, some values are cached for reuse in incremental compilation.
   /// Incremental compilation is basically calling [run] more than once.
   final bool hasIncrementalSupport;
@@ -965,6 +968,7 @@ abstract class Compiler implements DiagnosticListener {
             this.suppressWarnings: false,
             bool hasIncrementalSupport: false,
             this.enableAsyncAwait: false,
+            this.enableEnums: false,
             api.CompilerOutputProvider outputProvider,
             List<String> strips: const []})
       : this.disableTypeInferenceFlag =