Change analysis server protocol to omit empty lists when optional.

pkg/analysis_server/lib/src/services/correction/change.dart

Index: pkg/analysis_server/lib/src/services/correction/change.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/change.dart b/pkg/analysis_server/lib/src/services/correction/change.dart
index a20c00ec145ab7fd3a4b3cf927affbebddc6e7ac..04480c2834229f66176e22003db22a264120bef4 100644
--- a/pkg/analysis_server/lib/src/services/correction/change.dart
+++ b/pkg/analysis_server/lib/src/services/correction/change.dart
@@ -41,7 +41,7 @@ class Change implements HasToJson {
   void addEdit(String file, SourceEdit edit) {
     SourceFileEdit fileEdit = getFileEdit(file);
     if (fileEdit == null) {
-      fileEdit = new SourceFileEdit(file, <SourceEdit>[]);
+      fileEdit = new SourceFileEdit(file);
       addFileEdit(fileEdit);
     }
     fileEdit.add(edit);