Revert "Reduce use of Element in optimize.dart"

pkg/compiler/lib/src/ssa/interceptor_simplifier.dart

Index: pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
diff --git a/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart b/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
index e015e67a63fc1a78e6ed827dbcbaa0e452aa2961..2d6a1a7c513496c6ecff4e2e9840f1323eaac1b9 100644
--- a/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
+++ b/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
@@ -175,7 +175,7 @@ class SsaSimplifyInterceptors extends HBaseVisitor
       // code is completely insensitive to the specific instance subclasses, we
       // can use the non-leaf class directly.
       ClassElement element = type.singleClass(closedWorld);
-      if (element != null && backendClasses.isNativeClass(element)) {
+      if (element != null && backendClasses.isNative(element)) {
         return element;
       }
     }