Don't mangle private names.

test/kernel/regression/type_with_parse_error.dart.txt

Index: test/kernel/regression/type_with_parse_error.dart.txt
diff --git a/test/kernel/regression/type_with_parse_error.dart.txt b/test/kernel/regression/type_with_parse_error.dart.txt
index e004970d276b281f04cfd678415ba5c855b846af..18d0cca19bbcd65decb28363218f9e624896ffac 100644
--- a/test/kernel/regression/type_with_parse_error.dart.txt
+++ b/test/kernel/regression/type_with_parse_error.dart.txt
@@ -6,7 +6,7 @@ class A extends core::Object {
   constructor •() → self::A
     : super core::Object::•();
   method foo() → dynamic {
-    throw core::dart.core::_malformedTypeError("'B' is not a type.");
+    throw core::_malformedTypeError("'B' is not a type.");
   }
 }
 class B extends core::Object {
@@ -14,5 +14,5 @@ class B extends core::Object {
     : super core::Object::•();
 }
 static method main() → dynamic {
-  throw core::dart.core::_malformedTypeError("'B' is not a type.");
+  throw core::_malformedTypeError("'B' is not a type.");
 }