Revert "Native mixin interceptor bug fix"

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 074f1783d9000bea2a90179c6468a787a47943ff..7feb253ee3c6375dd5dbdd799c38e770855572b9 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -845,37 +845,12 @@ class JavaScriptBackend extends Backend {
       Set<ClassElement> result = new Set<ClassElement>();
       for (Element element in intercepted) {
         ClassElement classElement = element.getEnclosingClass();
-        if (classElement.isNative()
-            || interceptedClasses.contains(classElement)) {
-          result.add(classElement);
-        }
-        if (classesMixedIntoNativeClasses.contains(classElement)) {
-          Set<Element> nativeSubclasses = nativeSubclassesOfMixin(classElement);
-          if (nativeSubclasses != null) result.addAll(nativeSubclasses);
-        }
+        result.add(classElement);
       }
       return result;
     });
   }
 
-  Set<Element> nativeSubclassesOfMixin(ClassElement mixin) {
-    Set<MixinApplicationElement> uses = compiler.world.mixinUses[mixin];
-    if (uses == null) return null;
-    Set<Element> result = null;
-    for (MixinApplicationElement use in uses) {
-      Iterable<ClassElement> subclasses = compiler.world.subclasses[use];
-      if (subclasses != null) {
-        for (ClassElement subclass in subclasses) {
-          if (subclass.isNative()) {
-            if (result == null) result = new Set<Element>();
-            result.add(subclass);
-          }
-        }
-      }
-    }
-    return result;
-  }
-
   bool operatorEqHandlesNullArgument(FunctionElement operatorEqfunction) {
     return specialOperatorEqClasses.contains(
         operatorEqfunction.getEnclosingClass());