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

pkg/compiler/lib/src/elements/elements.dart

Index: pkg/compiler/lib/src/elements/elements.dart
diff --git a/pkg/compiler/lib/src/elements/elements.dart b/pkg/compiler/lib/src/elements/elements.dart
index 60fcb20f2663e0b8141bc271a121e0dfe9e8b9f3..29d9285ad40eab452f2e44d71edba30d455feb58 100644
--- a/pkg/compiler/lib/src/elements/elements.dart
+++ b/pkg/compiler/lib/src/elements/elements.dart
@@ -305,8 +305,6 @@ abstract class Element implements Entity {
   /// as all other classes.
   bool get isTopLevel;
   bool get isAssignable;
-  bool get isNative;
-  bool get isJsInterop;
 
   bool get isDeferredLoaderGetter;
 
@@ -401,11 +399,6 @@ abstract class Element implements Entity {
   bool get isSynthesized;
   bool get isMixinApplication;
 
-  bool get hasFixedBackendName;
-  String get fixedBackendName;
-
-  String get jsInteropName;
-
   bool get isAbstract;
 
   Scope buildScope();
@@ -415,9 +408,6 @@ abstract class Element implements Entity {
   AnalyzableElement get analyzableElement;
 
   accept(ElementVisitor visitor, arg);
-
-  void setJsInteropName(String name);
-  void markAsJsInterop();
 }
 
 class Elements {
@@ -520,13 +510,6 @@ class Elements {
         (element.isFunction || element.isAccessor);
   }
 
-  static bool isNativeOrExtendsNative(ClassElement element) {
-    if (element == null) return false;
-    if (element.isNative || element.isJsInterop) return true;
-    assert(element.isResolved);
-    return isNativeOrExtendsNative(element.superclass);
-  }
-
   static bool isInstanceSend(Send send, TreeElements elements) {
     Element element = elements[send];
     if (element == null) return !isClosureSend(send, element);
@@ -746,7 +729,7 @@ class Elements {
     constructor = constructor.effectiveTarget;
     ClassElement cls = constructor.enclosingClass;
     return cls.library == compiler.typedDataLibrary
-        && cls.isNative
+        && compiler.backend.isNative(cls)
         && compiler.world.isSubtypeOf(cls, compiler.typedDataClass)
         && compiler.world.isSubtypeOf(cls, compiler.listClass)
         && constructor.name == '';
@@ -904,7 +887,6 @@ abstract class LibraryElement extends Element
    */
   bool get isInternalLibrary;
 
-  bool get canUseNative;
   bool get exportsHandled;
 
   LibraryElement get implementation;
@@ -1394,8 +1376,6 @@ abstract class ClassElement extends TypeDeclarationElement
   ClassElement get declaration;
   ClassElement get implementation;
 
-  String get nativeTagInfo;
-
   /// `true` if this class is an enum declaration.
   bool get isEnumClass;