Add the @protected annotation

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 3a26bc461a243146003dd5e31048cc0effee8665..5474b6e0e1a228d3bfeaa76bc009f047f5525e15 100644
--- a/pkg/meta/lib/meta.dart
+++ b/pkg/meta/lib/meta.dart
@@ -21,3 +21,20 @@
  * in the language tour.
  */
 library meta;
+
+/**
+ * Used to annotate an instance method `m` in a class `C`. 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.
+ *
+ * Tools, such as the analyzer, can provide feedback if an invocation of a
+ * method marked as being protected is used outside of an instance method
+ * defined on a class that extends or mixes in the class in which the protected
+ * method is defined, or that uses a receiver other than `this`.
+ */

[Bob Nystrom, 2016/02/17 19:35:07]

I understand if analyzer uses /** */ for historical reasons, but this is a
separate package and should really follow the style guide.

Who knows, you may even eventually start liking "///". :)

[pquitslund, 2016/02/17 19:35:51]

Any chance we can jump to the future and adopt `///`-style comments?

[Brian Wilkerson, 2016/02/17 20:53:19]

As much as I prefer "/**" style comments, I was resigned to the need to bow to
the prevailing winds. Then I noticed that the file already used "/**" comments
for the library doc comment, so I went with the flow. Was I wrong to preserve
the already established style?

+const _Protected protected = const _Protected();
+
+class _Protected {
+  const _Protected();
+}