Capture more errors and improve duplicate error removal

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

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library test.src.task.dart_test;
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/constant.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ skipping 2086 matching lines @@
   test_buildInputs() {
     Map<String, TaskInput> inputs = LibraryUnitErrorsTask
         .buildInputs(new LibrarySpecificUnit(emptySource, emptySource));
     expect(inputs, isNotNull);
     expect(inputs.keys, unorderedEquals([
       LibraryUnitErrorsTask.BUILD_FUNCTION_TYPE_ALIASES_ERRORS_INPUT,
       LibraryUnitErrorsTask.CONSTRUCTORS_ERRORS_INPUT,
       LibraryUnitErrorsTask.HINTS_INPUT,
       LibraryUnitErrorsTask.RESOLVE_REFERENCES_ERRORS_INPUT,
       LibraryUnitErrorsTask.RESOLVE_TYPE_NAMES_ERRORS_INPUT,
+      LibraryUnitErrorsTask.VARIABLE_REFERENCE_ERRORS_INPUT,
       LibraryUnitErrorsTask.VERIFY_ERRORS_INPUT
     ]));
   }
 
   test_constructor() {
     LibraryUnitErrorsTask task =
         new LibraryUnitErrorsTask(context, emptySource);
     expect(task, isNotNull);
     expect(task.context, context);
     expect(task.target, emptySource);
@@ skipping 599 matching lines @@
   /**
    * Fill [errorListener] with [result] errors in the current [task].
    */
   void _fillErrorListener(ResultDescriptor<List<AnalysisError>> result) {
     List<AnalysisError> errors = task.outputs[result];
     expect(errors, isNotNull, reason: result.name);
     errorListener = new GatheringErrorListener();
     errorListener.addAll(errors);
   }
 }