Revert "Emit warning on import of dart:mirrors."

pkg/compiler/lib/src/warnings.dart

Index: pkg/compiler/lib/src/warnings.dart
diff --git a/pkg/compiler/lib/src/warnings.dart b/pkg/compiler/lib/src/warnings.dart
index b82a586dced4e810b97884686fa51e38216fb273..5d872d0106329df0c54e6cad4f495e7a2b76494a 100644
--- a/pkg/compiler/lib/src/warnings.dart
+++ b/pkg/compiler/lib/src/warnings.dart
@@ -2226,30 +2226,6 @@ main() sync* {
   // Patch errors end.
   //////////////////////////////////////////////////////////////////////////////
 
-  static const String IMPORT_EXPERIMENTAL_MIRRORS_PADDING = '\n*   ';
-
-  static const MessageKind IMPORT_EXPERIMENTAL_MIRRORS =
-      const MessageKind(r'''
-
-****************************************************************
-* WARNING: dart:mirrors support in dart2js is experimental,
-*          and not recommended.
-*          This implementation of mirrors is incomplete,
-*          and often greatly increases the size of the generated
-*          JavaScript code.
-*
-* Your app imports dart:mirrors via:''''''
-$IMPORT_EXPERIMENTAL_MIRRORS_PADDING#{importChain}
-*
-* Starting with Dart 1.8, you must use the
-* --enable-experimental-mirrors command-line flag to opt-in.
-* You can begin using this flag now if mirrors support is critical.
-*
-* To learn what to do next, please visit:
-*    http://dartlang.org/dart2js-reflection
-****************************************************************
-''');
-
   static const MessageKind CALL_NOT_SUPPORTED_ON_NATIVE_CLASS =
       const MessageKind(
           "Non-supported 'call' member on a native class, or a "