First set of test triage for fast-startup

tests/html/html.status

Index: tests/html/html.status
diff --git a/tests/html/html.status b/tests/html/html.status
index 36c0e8ab5ebdef724b30cbc780598588b43b992f..311827b427f50d4546471f87a7c6ba459d1d707a 100644
--- a/tests/html/html.status
+++ b/tests/html/html.status
@@ -411,6 +411,12 @@ webgl_1_test: StaticWarning
 window_nosuchmethod_test: StaticWarning
 js_typed_interop_default_arg_test/default_value: MissingCompileTimeError # Issue #25759
 
+[ $compiler == dart2js && $fast_startup ]
+custom/constructor_calls_created_synchronously_test: Fail # mirrors not supported
+custom/js_custom_test: Fail # mirrors not supported
+custom/mirrors_test: Fail # mirrors not supported
+mirrors_js_typed_interop_test: Fail # mirrors not supported
+
 [ $compiler == dart2js && $cps_ir && $browser ]
 js_typed_interop_side_cast_exp_test: RuntimeError # Corner case in package:js that we might want to remove (See comment in #24978).
 js_typed_interop_test/static_method_tearoff_1: RuntimeError # Tree-shaking a used tear-off (#24978, #25720).