Plumb "enableSuperMixins" option through analysis server (implements DEP 34).

pkg/analysis_server/lib/src/get_handler.dart

Index: pkg/analysis_server/lib/src/get_handler.dart
diff --git a/pkg/analysis_server/lib/src/get_handler.dart b/pkg/analysis_server/lib/src/get_handler.dart
index 360b5daffce8353c7aa7bad62d9c3c89d20404bb..7300d102610ae12da6155477397d141da584bea2 100644
--- a/pkg/analysis_server/lib/src/get_handler.dart
+++ b/pkg/analysis_server/lib/src/get_handler.dart
@@ -1054,6 +1054,7 @@ class GetHandler {
       _writeOption(buffer, 'Cache size', options.cacheSize);
       _writeOption(
           buffer, 'Enable strict call checks', options.enableStrictCallChecks);
+      _writeOption(buffer, 'Enable super mixins', options.enableSuperMixins);
       _writeOption(buffer, 'Generate hints', options.hint);
       _writeOption(buffer, 'Generate dart2js hints', options.dart2jsHint);
       _writeOption(buffer, 'Generate errors in implicit files',