Fix "ignore:" handling with upper case error codes.

pkg/analyzer/test/generated/error_suppression_test.dart

 // Copyright (c) 2016, 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.
 
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 
 import '../reflective_tests.dart';
 import '../utils.dart';
@@ skipping 64 matching lines @@
   void test_ignore_second_trailing() {
     Source source = addSource('''
 //INVALID_ASSIGNMENT
 int x = '';
 const y = x; // ignore: const_initialized_with_non_constant_value
 ''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [StaticTypeWarningCode.INVALID_ASSIGNMENT]);
   }
 
+  void test_ignore_upper_case() {
+    Source source = addSource('''
+int x = ''; // ignore: INVALID_ASSIGNMENT
+''');
+    computeLibrarySourceErrors(source);
+    assertErrors(source, []);
+  }
+
   void test_invalid_error_code() {
     Source source = addSource('''
 // ignore: right_format_wrong_code
 int x = '';
 const y = x; //CONST_INITIALIZED_WITH_NON_CONSTANT_VALUE
 ''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [
       StaticTypeWarningCode.INVALID_ASSIGNMENT,
       CompileTimeErrorCode.CONST_INITIALIZED_WITH_NON_CONSTANT_VALUE
@@ skipping 86 matching lines @@
 int x = '';  //INVALID_ASSIGNMENT
 const y = x; //CONST_INITIALIZED_WITH_NON_CONSTANT_VALUE
 ''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [
       StaticTypeWarningCode.INVALID_ASSIGNMENT,
       CompileTimeErrorCode.CONST_INITIALIZED_WITH_NON_CONSTANT_VALUE
     ]);
   }
 }