Defer addStubs to class instantiation time.

pkg/compiler/lib/src/js_backend/backend.dart

Index: pkg/compiler/lib/src/js_backend/backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend.dart b/pkg/compiler/lib/src/js_backend/backend.dart
index 1ed077da32f754dbdefa76b2a66c7b3bbd76fb52..b67f61d81addfdcb8913e81b7e0be2c54032577e 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -694,7 +694,7 @@ class JavaScriptBackend extends Backend {
    * Record that [method] is called from a subclass via `super`.
    */
   bool maybeRegisterAliasedSuperMember(Element member, Selector selector) {
-    if (selector.isGetter || compiler.hasIncrementalSupport) {
+    if (!canUseAliasedSuperMember(member, selector)) {
       // Invoking a super getter isn't supported, this would require changes to
       // compact field descriptors in the emitter.
       // We also turn off this optimization in incremental compilation, to
@@ -706,6 +706,10 @@ class JavaScriptBackend extends Backend {
     return true;
   }
 
+  bool canUseAliasedSuperMember(Element member, Selector selector) {
+    return !selector.isGetter && !compiler.hasIncrementalSupport;
+  }
+
   /**
    * Returns `true` if [member] is called from a subclass via `super`.
    */