Encode super calls via extra properties on prototypes.

sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
index dfd5a92a974849f20cdaecc6a8e44d7428143636..0f01f9c86572926652e2c1bf78a4637cc4c23fd5 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -323,6 +323,12 @@ class JavaScriptBackend extends Backend {
    */
   final Set<ClassElement> specialOperatorEqClasses = new Set<ClassElement>();
 
+  /**
+   * A set of members that are called from subclasses via super.
+   */
+  final Set<FunctionElement> aliasedSuperMembers =
+      new Setlet<FunctionElement>();
+
   List<CompilerTask> get tasks {
     return <CompilerTask>[builder, optimizer, generator, emitter];
   }
@@ -528,6 +534,20 @@ class JavaScriptBackend extends Backend {
     return name;
   }
 
+  /**
+   * Record that [method] is called from a subclass via `super`.
+   */
+  void registerAliasedSuperMember(FunctionElement method) {
+    aliasedSuperMembers.add(method);
+  }
+
+  /**
+   * Returns `true` is [member] is called from a subclass via `super`.
+   */
+  bool isAliasedSuperMember(FunctionElement member) {
+    return aliasedSuperMembers.contains(member);
+  }
+
   bool isInterceptedMethod(Element element) {
     if (!element.isInstanceMember) return false;
     if (element.isGenerativeConstructorBody) {