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 08fa0a74db29be482239a6f7e62b6111c4bfc36d..61701c3e9f2cc2f6c9499f4d36fa7ef1c0bb801c 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -702,7 +702,7 @@ 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
@@ -714,6 +714,10 @@ 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`.
    */