Revert "Reduce use of Element in optimize.dart"

pkg/compiler/lib/src/js_backend/backend.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library js_backend.backend;
 
 import 'dart:async' show Future;
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
 
@@ skipping 775 matching lines @@
   bool isJsInterop(Element element) => nativeData.isJsInterop(element);
 
   /// Whether [element] corresponds to a native JavaScript construct either
   /// through the native mechanism (`@Native(...)` or the `native` pseudo
   /// keyword) which is only allowed for internal libraries or via the typed
   /// JavaScriptInterop mechanism which is allowed for user libraries.
   @override
   bool isNative(Entity element) => nativeData.isNative(element);
 
   /// Returns the [NativeBehavior] for calling the native [method].
-  native.NativeBehavior getNativeMethodBehavior(MethodElement method) {
+  native.NativeBehavior getNativeMethodBehavior(FunctionElement method) {
     return nativeData.getNativeMethodBehavior(method);
   }
 
   /// Returns the [NativeBehavior] for reading from the native [field].
   native.NativeBehavior getNativeFieldLoadBehavior(FieldElement field) {
     return nativeData.getNativeFieldLoadBehavior(field);
   }
 
   /// Returns the [NativeBehavior] for writing to the native [field].
   native.NativeBehavior getNativeFieldStoreBehavior(FieldElement field) {
@@ skipping 2457 matching lines @@
         classElement == helpers.jsInterceptorClass ||
         classElement == helpers.jsNullClass;
   }
 
   @override
   bool isInterceptorClass(ClassElement cls) {
     return helpers.backend.isInterceptorClass(cls);
   }
 
   @override
-  bool isNativeClass(ClassElement element) {
-    return helpers.backend.isNative(element);
-  }
-
-  @override
-  bool isNativeMember(MemberElement element) {
+  bool isNative(Element element) {
     return helpers.backend.isNative(element);
   }
 }