Extend @protected to include implemented interfaces.

pkg/meta/lib/meta.dart

Index: pkg/meta/lib/meta.dart
diff --git a/pkg/meta/lib/meta.dart b/pkg/meta/lib/meta.dart
index ff0f9b0d87e23285d63fc6749f2a80501306e73c..17f7f1f6d86b6d4cdbd1f1d291f13ad10b168b82 100644
--- a/pkg/meta/lib/meta.dart
+++ b/pkg/meta/lib/meta.dart
@@ -69,8 +69,9 @@ const _OptionalTypeArgs optionalTypeArgs = const _OptionalTypeArgs();
 /// field) `m` in a class `C`. If the annotation is on a field it applies to the
 /// getter, and setter if appropriate, that are induced by the field. Indicates
 /// that `m` should only be invoked from instance methods of `C` or classes that
-/// extend or mix in `C`, either directly or indirectly. Additionally indicates
-/// that `m` should only be invoked on `this`, whether explicitly or implicitly.
+/// extend, implement or mix in `C`, either directly or indirectly. Additionally
+/// indicates that `m` should only be invoked on `this`, whether explicitly or
+/// implicitly.
 ///
 /// Tools, such as the analyzer, can provide feedback if
 ///