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

pkg/analyzer/lib/src/task/dart.dart

Index: pkg/analyzer/lib/src/task/dart.dart
diff --git a/pkg/analyzer/lib/src/task/dart.dart b/pkg/analyzer/lib/src/task/dart.dart
index 1d806bd77d4b56ae72fe81561b9857fee9446410..5abd691a31489ff9db1a37e6735f3e1f22d5cd24 100644
--- a/pkg/analyzer/lib/src/task/dart.dart
+++ b/pkg/analyzer/lib/src/task/dart.dart
@@ -3169,8 +3169,10 @@ class IgnoreInfo {
     IgnoreInfo ignoreInfo = new IgnoreInfo();
     for (Match match in matches) {
       // See _IGNORE_MATCHER for format --- note the possibility of error lists.
-      Iterable<String> codes =
-          match.group(1).split(',').map((String code) => code.trim());
+      Iterable<String> codes = match
+          .group(1)
+          .split(',')
+          .map((String code) => code.trim().toLowerCase());
       ignoreInfo.addAll(info.getLocation(match.start).lineNumber, codes);
     }
     return ignoreInfo;