Ensure constructorName symbols include private manglings.

runtime/lib/mirrors_patch.dart

Index: runtime/lib/mirrors_patch.dart
diff --git a/runtime/lib/mirrors_patch.dart b/runtime/lib/mirrors_patch.dart
index b3f2d4d530907dc4328caa590c307ab8ec493c58..97e60ceb169e57166b8531341e27a85a228b6253 100644
--- a/runtime/lib/mirrors_patch.dart
+++ b/runtime/lib/mirrors_patch.dart
@@ -48,12 +48,17 @@ patch TypeMirror reflectType(Type key) {
 patch class MirrorSystem {
   /* patch */ static String getName(Symbol symbol) {
     String string = _symbol_dev.Symbol.getName(symbol);
-    if (string.contains(' with ')) return string;
+    if (string.contains(' with ')) {
+      // Constructor names of anonymous mixin applications
+      var at_pos = string.indexOf('@');
+      if (at_pos == -1) return string;
+      return string.substring(0, at_pos);
+    }
     return _unmangleName(string);
   }
   /* patch */ static Symbol getSymbol(String name, [LibraryMirror library]) {
     if (library is! LibraryMirror ||
-        ((name[0] == '_') && (library == null))) {
+        ((name.length > 0) && (name[0] == '_') && (library == null))) {
       throw new ArgumentError(library);
     }
     if (library != null) name = _mangleName(name, library._reflectee);