Change analysis server protocol to omit empty lists when optional.

pkg/analysis_server/test/edit/assists_test.dart

Index: pkg/analysis_server/test/edit/assists_test.dart
diff --git a/pkg/analysis_server/test/edit/assists_test.dart b/pkg/analysis_server/test/edit/assists_test.dart
index df8fb7203b72bab2fc7c5acd5e90d3cf1a81a338..c343825d017c048129980bf64702a0baacb77245 100644
--- a/pkg/analysis_server/test/edit/assists_test.dart
+++ b/pkg/analysis_server/test/edit/assists_test.dart
@@ -41,8 +41,7 @@ class AssistsTest extends AbstractAnalysisTest {
     changes = sourceChangeList.map((SourceChange sourceChange) {
       Change change = new Change(sourceChange.message);
       sourceChange.edits.forEach((SourceFileEdit sourceFileEdit) {
-        SourceFileEdit fileEdit = new SourceFileEdit(sourceFileEdit.file,
-            <SourceEdit>[]);
+        SourceFileEdit fileEdit = new SourceFileEdit(sourceFileEdit.file);
         change.fileEdits.add(fileEdit);
         fileEdit.edits.addAll(sourceFileEdit.edits);
       });