Move native and js interop properties from the element model to the JS backend

pkg/compiler/lib/src/common/backend_api.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 dart2js.backend_api;
 
 import 'dart:async' show Future;
 
 import '../common.dart';
 import '../compiler.dart' show
@@ skipping 25 matching lines @@
 import '../io/code_output.dart' show
     CodeBuffer;
 import '../io/source_information.dart' show
     SourceInformationStrategy;
 import '../js_backend/js_backend.dart' as js_backend show
     JavaScriptBackend;
 import '../library_loader.dart' show
     LibraryLoader,
     LoadedLibraries;
 import '../native/native.dart' as native show
-    NativeEnqueuer;
+    NativeEnqueuer,
+    maybeEnableNative;
 import '../patch_parser.dart' show
     checkNativeAnnotation, checkJsInteropAnnotation;
 import '../resolution/tree_elements.dart' show
     TreeElements;
 import '../tree/tree.dart' show
     Node,
     Send;
 import '../universe/call_structure.dart' show
     CallStructure;
 
@@ skipping 195 matching lines @@
   ClassElement get positiveIntImplementation => compiler.intClass;
 
   ClassElement defaultSuperclass(ClassElement element) => compiler.objectClass;
 
   bool isInterceptorClass(ClassElement element) => false;
 
   /// Returns `true` if [element] is a foreign element, that is, that the
   /// backend has specialized handling for the element.
   bool isForeign(Element element) => false;
 
+  /// Returns `true` if [element] is a native element, that is, that the
+  /// corresponding entity already exists in the target language.
+  bool isNative(Element element) => false;
+
+  /// Returns `true` if [element] is implemented via typed JavaScript interop.
+  // TODO(johnniwinther): Move this to [JavaScriptBackend].
+  bool isJsInterop(Element element) => false;
+
+  /// Returns `true` if the `native` pseudo keyword is supported for [library].
+  bool canLibraryUseNative(LibraryElement library) {
+    // TODO(johnniwinther): Move this to [JavaScriptBackend].
+    return native.maybeEnableNative(compiler, library);
+  }
+
   /// Processes [element] for resolution and returns the [FunctionElement] that
   /// defines the implementation of [element].
   FunctionElement resolveExternalFunction(FunctionElement element) => element;
 
   /// Returns `true` if [library] is a backend specific library whose members
   /// have special treatment, such as being allowed to extends blacklisted
   /// classes or member being eagerly resolved.
   bool isBackendLibrary(LibraryElement library) {
     // TODO(johnniwinther): Remove this when patching is only done by the
     // JavaScript backend.
     Uri canonicalUri = library.canonicalUri;
     if (canonicalUri == js_backend.JavaScriptBackend.DART_JS_HELPER ||
         canonicalUri == js_backend.JavaScriptBackend.DART_INTERCEPTORS) {
       return true;
     }
     return false;
   }
 
   void registerStaticUse(Element element, Enqueuer enqueuer) {}
 
   /// This method is called immediately after the [LibraryElement] [library] has
   /// been created.
   void onLibraryCreated(LibraryElement library) {}
 
   /// This method is called immediately after the [library] and its parts have
   /// been scanned.
   Future onLibraryScanned(LibraryElement library, LibraryLoader loader) {
-    if (library.canUseNative) {
+    // TODO(johnniwinther): Move this to [JavaScriptBackend].
+    if (canLibraryUseNative(library)) {
       library.forEachLocalMember((Element element) {
         if (element.isClass) {
           checkNativeAnnotation(compiler, element);
         }
       });
     }
     checkJsInteropAnnotation(compiler, library);
     library.forEachLocalMember((Element element) {
       checkJsInteropAnnotation(compiler, element);
-      if (element.isClass && element.isJsInterop) {
+      if (element.isClass && isJsInterop(element)) {
         ClassElement classElement = element;
         classElement.forEachMember((_, memberElement) {
           checkJsInteropAnnotation(compiler, memberElement);
         });
       }
     });
     return new Future.value();
   }
 
   /// This method is called when all new libraries loaded through
@@ skipping 92 matching lines @@
   /// Returns the constant expression of [node], or `null` if [node] is not
   /// a constant expression.
   ConstantExpression getConstant(Node node);
 
   /// Registers [type] as instantiated.
   void registerInstantiatedType(InterfaceType type);
 
   /// Resolves [typeName] to a type in the context of [node].
   DartType resolveTypeFromString(Node node, String typeName);
 }