Encode super calls via extra properties on prototypes.

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 c2166d4ce291799971b5a626faa37f1748727cd5..75238e4afa7d0c13f0826c011d8b72b76aa08c14 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -331,6 +331,12 @@ 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 {
     List<CompilerTask> result = functionCompiler.tasks;
     result.add(emitter);
@@ -548,6 +554,20 @@ 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` if [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) {
@@ -2259,6 +2279,7 @@ class JavaScriptBackend extends Backend {
   void forgetElement(Element element) {
     constants.forgetElement(element);
     constantCompilerTask.dartConstantCompiler.forgetElement(element);
+    aliasedSuperMembers.remove(element);
   }
 
   void registerMainHasArguments(Enqueuer enqueuer) {