Address a number of issues related to computation of currentScript and deferred loading.

dart/tests/compiler/dart2js_native/dart2js_native.status

Index: dart/tests/compiler/dart2js_native/dart2js_native.status
diff --git a/dart/tests/compiler/dart2js_native/dart2js_native.status b/dart/tests/compiler/dart2js_native/dart2js_native.status
index cb7557dbfd32f550a05ef7119145bbe850b7317a..0191a101c587e89cfc341aaf67984b4d4b85ed20 100644
--- a/dart/tests/compiler/dart2js_native/dart2js_native.status
+++ b/dart/tests/compiler/dart2js_native/dart2js_native.status
@@ -8,3 +8,9 @@
 [ $compiler == dart2js ]
 native_no_such_method_exception4_frog_test: Fail  # Issue 9631
 native_no_such_method_exception5_frog_test: Fail  # Issue 9631
+
+[ $browser || $runtime == jsshell ]
+only_pass_on_d8_test: Fail, OK # This test should only pass on D8.
+
+[ $browser || $runtime == d8 ]
+only_pass_on_jsshell_test: Fail, OK # This test should only pass on jsshell.