Make minification Entity-friendly.

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

Index: pkg/compiler/lib/src/js_backend/field_naming_mixin.dart
diff --git a/pkg/compiler/lib/src/js_backend/field_naming_mixin.dart b/pkg/compiler/lib/src/js_backend/field_naming_mixin.dart
index a213223f8bea5168bec2863a0367ab439e946e66..3405339113f3890066fbbaf48308796da24d1a94 100644
--- a/pkg/compiler/lib/src/js_backend/field_naming_mixin.dart
+++ b/pkg/compiler/lib/src/js_backend/field_naming_mixin.dart
@@ -13,7 +13,7 @@ abstract class _MinifiedFieldNamer implements Namer {
   // The inheritance scope based naming might not yield a name. For instance,
   // this could be because the field belongs to a mixin. In such a case this
   // will return `null` and a normal field name has to be used.
-  jsAst.Name _minifiedInstanceFieldPropertyName(FieldElement element) {
+  jsAst.Name _minifiedInstanceFieldPropertyName(FieldEntity element) {
     if (_nativeData.hasFixedBackendName(element)) {
       return new StringBackedName(_nativeData.getFixedBackendName(element));
     }
@@ -21,8 +21,10 @@ abstract class _MinifiedFieldNamer implements Namer {
     _FieldNamingScope names;
     if (element is BoxFieldElement) {
       names = new _FieldNamingScope.forBox(element.box, fieldRegistry);
+    } else if (element is JBoxedField) {
+      names = new _FieldNamingScope.forBox(element.box, fieldRegistry);
     } else {
-      ClassElement cls = element.enclosingClass;
+      ClassEntity cls = element.enclosingClass;
       names = new _FieldNamingScope.forClass(cls, _closedWorld, fieldRegistry);
     }
 
@@ -116,19 +118,20 @@ class _FieldNamingScope {
   }
 
   factory _FieldNamingScope.forClass(
-      ClassElement cls, ClosedWorld world, _FieldNamingRegistry registry) {
+      ClassEntity cls, ClosedWorld world, _FieldNamingRegistry registry) {
     _FieldNamingScope result = registry.scopes[cls];
     if (result != null) return result;
 
     if (world.isUsedAsMixin(cls)) {
       result = new _MixinFieldNamingScope.mixin(cls, registry);
     } else {
-      if (cls.superclass == null) {
+      var superclass = world.elementEnvironment.getSuperClass(cls);
+      if (superclass == null) {
         result = new _FieldNamingScope.rootScope(cls, registry);
       } else {
         _FieldNamingScope superScope =
-            new _FieldNamingScope.forClass(cls.superclass, world, registry);
-        if (cls.isMixinApplication) {
+            new _FieldNamingScope.forClass(superclass, world, registry);
+        if (world.elementEnvironment.isMixinApplication(cls)) {
           result =
               new _MixinFieldNamingScope.mixedIn(cls, superScope, registry);
         } else {
@@ -137,7 +140,10 @@ class _FieldNamingScope {
       }
     }
 
-    cls.forEachInstanceField((cls, field) => result.add(field));
+    world.elementEnvironment.forEachClassMember(cls,
+        (ClassEntity declarer, MemberEntity member) {
+      if (member.isField && member.isInstanceMember) result.add(member);
+    });
 
     registry.scopes[cls] = result;
     return result;
@@ -166,13 +172,13 @@ class _FieldNamingScope {
 
   jsAst.Name _nextName() => registry.getName(_localFieldNameCounter++);
 
-  jsAst.Name operator [](Element field) {
+  jsAst.Name operator [](Entity field) {
     jsAst.Name name = names[field];
     if (name == null && superScope != null) return superScope[field];
     return name;
   }
 
-  void add(Element field) {
+  void add(Entity field) {
     if (names.containsKey(field)) return;
 
     jsAst.Name value = _nextName();
@@ -180,7 +186,7 @@ class _FieldNamingScope {
     names[field] = value;
   }
 
-  bool containsField(Element field) => names.containsKey(field);
+  bool containsField(Entity field) => names.containsKey(field);
 }
 
 /**
@@ -227,7 +233,7 @@ class _BoxFieldNamingScope extends _FieldNamingScope {
   @override
   bool containsField(_) => true;
 
-  jsAst.Name operator [](Element field) {
+  jsAst.Name operator [](Entity field) {
     if (!names.containsKey(field)) add(field);
     return names[field];
   }