Add proper API for creating private symbols wrt a library.

tests/lib/lib.status

Index: tests/lib/lib.status
diff --git a/tests/lib/lib.status b/tests/lib/lib.status
index 80e5ab024c322191ae30d47328f0b8f637b9df87..e05a16016d97810e1ea8f27e6f7e115d68e1cf2f 100644
--- a/tests/lib/lib.status
+++ b/tests/lib/lib.status
@@ -12,6 +12,8 @@ mirrors/fake_function_test: RuntimeError # Issue 11612
 mirrors/function_type_mirror_test: RuntimeError # Issue 12166
 mirrors/generics_test/01: RuntimeError # Issue 12333
 mirrors/hierarchy_invariants_test: RuntimeError # Issue 11863
+mirrors/intercepted_class_test: RuntimeError # Issue 13644
+mirrors/intercepted_object_test: RuntimeError # Issue 13644
 mirrors/invoke_test: RuntimeError # Issue 11954
 mirrors/invoke_closurization_test: RuntimeError # Issue 13002
 mirrors/invoke_named_test/none: RuntimeError # Issue 12863
@@ -40,8 +42,9 @@ mirrors/redirecting_factory_test/none: RuntimeError # Issue 6490
 mirrors/redirecting_factory_test/02: RuntimeError # Issue 6490
 mirrors/closures_test/none: RuntimeError # Issue 6490
 mirrors/library_metadata2_test/01: CompileTimeError # Issue 13633
-
 async/stream_controller_async_test: Pass, Fail # Issue 13608
+mirrors/symbol_validation_test: RuntimeError # Issue 13597
+mirrors/private_symbol_test: CompileTimeError # Issue 13597
 
 [ $runtime == safari ]
 mirrors/return_type_test: Pass, Timeout # Issue 12858
@@ -143,7 +146,7 @@ mirrors/typedef_test/01: Fail, OK # Incorrect dart2js behavior.
 mirrors/redirecting_factory_test/none: Fail # Issue 13365
 mirrors/redirecting_factory_test/01: Fail # Issue 13365
 mirrors/redirecting_factory_test/02: Fail # Issue 13365
-mirrors/closures_test/01: Fail, OK # Incorrect dart2js behavior.
+mirrors/symbol_validation_test: RuntimeError # Issue 13596
 
 [ $compiler == none && $runtime == drt ]
 async/timer_isolate_test: Skip # See Issue 4997