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

pkg/analyzer/test/generated/error_suppression_test.dart

Index: pkg/analyzer/test/generated/error_suppression_test.dart
diff --git a/pkg/analyzer/test/generated/error_suppression_test.dart b/pkg/analyzer/test/generated/error_suppression_test.dart
index 275e94ccc54468a5fdb35f8bda42547aaf2687eb..edcfaf2b254dc520a2cc523e70d29bc40e98e440 100644
--- a/pkg/analyzer/test/generated/error_suppression_test.dart
+++ b/pkg/analyzer/test/generated/error_suppression_test.dart
@@ -82,6 +82,14 @@ const y = x; // ignore: const_initialized_with_non_constant_value
     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