Access NativeData only through ClosedWorld

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

Index: pkg/compiler/lib/src/js_backend/native_data.dart
diff --git a/pkg/compiler/lib/src/js_backend/native_data.dart b/pkg/compiler/lib/src/js_backend/native_data.dart
index 67f495368e14d6ae2a612d3bef18f33a62ed3703..0ad4565e6a93b4f820a0300ad29816ddd9bd62e6 100644
--- a/pkg/compiler/lib/src/js_backend/native_data.dart
+++ b/pkg/compiler/lib/src/js_backend/native_data.dart
@@ -146,6 +146,9 @@ abstract class NativeDataBuilder {
 
   /// Sets the explicit js interop [name] for the member [element].
   void setJsInteropMemberName(MemberEntity element, String name);
+
+  /// Closes this builder and creates the resulting [NativeData] object.
+  NativeData close();
 }
 
 class NativeBasicDataBuilderImpl implements NativeBasicDataBuilder {
@@ -251,11 +254,7 @@ class NativeBasicDataImpl implements NativeBasicData {
   }
 }
 
-class NativeDataImpl implements NativeDataBuilder, NativeData {
-  /// Prefix used to escape JS names that are not valid Dart names
-  /// when using JSInterop.
-  static const String _jsInteropEscapePrefix = r'JS$';
-
+class NativeDataBuilderImpl implements NativeDataBuilder {
   final NativeBasicData _nativeBasicData;
 
   /// The JavaScript names for native JavaScript elements implemented.
@@ -273,17 +272,22 @@ class NativeDataImpl implements NativeDataBuilder, NativeData {
   Map<MemberEntity, NativeBehavior> nativeFieldStoreBehavior =
       <FieldEntity, NativeBehavior>{};
 
-  /// The JavaScript names for elements implemented via typed JavaScript
+  /// The JavaScript names for libraries implemented via typed JavaScript
   /// interop.
   Map<LibraryEntity, String> jsInteropLibraryNames = <LibraryEntity, String>{};
+
+  /// JavaScript interop classes annotated with `@anonymous`
   Set<ClassEntity> anonymousJsInteropClasses = new Set<ClassEntity>();
+
+  /// The JavaScript names for classes implemented via typed JavaScript
+  /// interop.
   Map<ClassEntity, String> jsInteropClassNames = <ClassEntity, String>{};
 
-  /// The JavaScript names for elements implemented via typed JavaScript
+  /// The JavaScript names for members implemented via typed JavaScript
   /// interop.
   Map<MemberEntity, String> jsInteropMemberNames = <MemberEntity, String>{};
 
-  NativeDataImpl(this._nativeBasicData);
+  NativeDataBuilderImpl(this._nativeBasicData);
 
   /// Sets the native [name] for the member [element]. This name is used for
   /// [element] in the generated JavaScript.
@@ -323,11 +327,6 @@ class NativeDataImpl implements NativeDataBuilder, NativeData {
   }
 
   @override
-  bool isAnonymousJsInteropClass(ClassEntity element) {
-    return anonymousJsInteropClasses.contains(element);
-  }
-
-  @override
   void markJsInteropClassAsAnonymous(ClassEntity element) {
     anonymousJsInteropClasses.add(element);
   }
@@ -345,19 +344,77 @@ class NativeDataImpl implements NativeDataBuilder, NativeData {
     jsInteropMemberNames[element] = null;
   }
 
-  /// Returns `true` if [element] is explicitly marked as part of JsInterop.
-  bool _isJsInteropMember(MemberEntity element) {
-    return jsInteropMemberNames.containsKey(element);
-  }
-
   /// Sets the explicit js interop [name] for the member [element].
   void setJsInteropMemberName(MemberEntity element, String name) {
-    assert(invariant(element, _isJsInteropMember(element),
+    assert(invariant(element, jsInteropMemberNames.containsKey(element),
         message:
             'Member $element is not js interop but given a js interop name.'));
     jsInteropMemberNames[element] = name;
   }
 
+  @override
+  NativeData close() => new NativeDataImpl(
+      _nativeBasicData,
+      nativeMemberName,
+      nativeMethodBehavior,
+      nativeFieldLoadBehavior,
+      nativeFieldStoreBehavior,
+      jsInteropLibraryNames,
+      anonymousJsInteropClasses,
+      jsInteropClassNames,
+      jsInteropMemberNames);
+}
+
+class NativeDataImpl implements NativeData {
+  /// Prefix used to escape JS names that are not valid Dart names
+  /// when using JSInterop.
+  static const String _jsInteropEscapePrefix = r'JS$';
+
+  final NativeBasicData _nativeBasicData;
+
+  /// The JavaScript names for native JavaScript elements implemented.
+  final Map<MemberEntity, String> nativeMemberName;
+
+  /// Cache for [NativeBehavior]s for calling native methods.
+  final Map<FunctionEntity, NativeBehavior> nativeMethodBehavior;
+
+  /// Cache for [NativeBehavior]s for reading from native fields.
+  final Map<MemberEntity, NativeBehavior> nativeFieldLoadBehavior;
+
+  /// Cache for [NativeBehavior]s for writing to native fields.
+  final Map<MemberEntity, NativeBehavior> nativeFieldStoreBehavior;
+
+  /// The JavaScript names for libraries implemented via typed JavaScript
+  /// interop.
+  final Map<LibraryEntity, String> jsInteropLibraryNames;
+
+  /// JavaScript interop classes annotated with `@anonymous`
+  final Set<ClassEntity> anonymousJsInteropClasses;
+
+  /// The JavaScript names for classes implemented via typed JavaScript
+  /// interop.
+  final Map<ClassEntity, String> jsInteropClassNames;
+
+  /// The JavaScript names for members implemented via typed JavaScript
+  /// interop.
+  final Map<MemberEntity, String> jsInteropMemberNames;
+
+  NativeDataImpl(
+      this._nativeBasicData,
+      this.nativeMemberName,
+      this.nativeMethodBehavior,
+      this.nativeFieldLoadBehavior,
+      this.nativeFieldStoreBehavior,
+      this.jsInteropLibraryNames,
+      this.anonymousJsInteropClasses,
+      this.jsInteropClassNames,
+      this.jsInteropMemberNames);
+
+  @override
+  bool isAnonymousJsInteropClass(ClassEntity element) {
+    return anonymousJsInteropClasses.contains(element);
+  }
+
   /// Returns `true` if [cls] is a native class.
   bool isNativeClass(ClassEntity element) =>
       _nativeBasicData.isNativeClass(element);
@@ -399,6 +456,11 @@ class NativeDataImpl implements NativeDataBuilder, NativeData {
     return jsInteropMemberNames[element];
   }
 
+  /// Returns `true` if [element] is explicitly marked as part of JsInterop.
+  bool _isJsInteropMember(MemberEntity element) {
+    return jsInteropMemberNames.containsKey(element);
+  }
+
   /// Returns `true` if [element] is a JsInterop method.
   bool isJsInteropMember(MemberEntity element) {
     if (element.isFunction ||