Use a transformer to initialize custom elements and call initMethod. This is the

pkg/polymer/test/build/all_phases_test.dart

Index: pkg/polymer/test/build/all_phases_test.dart
diff --git a/pkg/polymer/test/build/all_phases_test.dart b/pkg/polymer/test/build/all_phases_test.dart
index bb39a8549c877cf0de4b2c5bf8de7252132ac80e..3f84593bbe7cedcb49b7c4d36fcd90602d81cf0e 100644
--- a/pkg/polymer/test/build/all_phases_test.dart
+++ b/pkg/polymer/test/build/all_phases_test.dart
@@ -49,7 +49,6 @@ void main() {
 
           void main() {
             configureForDeployment([
-                'a.dart',
               ]);
             i0.main();
           }
@@ -77,7 +76,6 @@ void main() {
 
           void main() {
             configureForDeployment([
-                'test.html.0.dart',
               ]);
             i0.main();
           }
@@ -119,7 +117,6 @@ void main() {
 
           void main() {
             configureForDeployment([
-                'a.dart',
               ]);
             i0.main();
           }
@@ -158,8 +155,6 @@ void main() {
 
           void main() {
             configureForDeployment([
-                'test2.html.0.dart',
-                'b.dart',
               ]);
             i1.main();
           }