Removed CLASS_ELEMENTS from BuildCompilationUnitElementTask and cleaned up comments

pkg/analyzer/test/src/task/dart_test.dart

Index: pkg/analyzer/test/src/task/dart_test.dart
diff --git a/pkg/analyzer/test/src/task/dart_test.dart b/pkg/analyzer/test/src/task/dart_test.dart
index 6b64a374ae6cd4a915189fdae0efa11f9f9bd31c..d48469d000029ca5c5dc0ac84b46b703d860fa01 100644
--- a/pkg/analyzer/test/src/task/dart_test.dart
+++ b/pkg/analyzer/test/src/task/dart_test.dart
@@ -205,8 +205,7 @@ part 'part.dart';
 class A {}
 class B = Object with A;
 ''');
-    expect(outputs, hasLength(3));
-    expect(outputs[CLASS_ELEMENTS], hasLength(2));
+    expect(outputs, hasLength(2));
     expect(outputs[COMPILATION_UNIT_ELEMENT], isNotNull);
     expect(outputs[RESOLVED_UNIT1], isNotNull);
   }