Convert data objects eagerly from K to J

pkg/compiler/lib/src/kernel/element_map_impl.dart

Index: pkg/compiler/lib/src/kernel/element_map_impl.dart
diff --git a/pkg/compiler/lib/src/kernel/element_map_impl.dart b/pkg/compiler/lib/src/kernel/element_map_impl.dart
index 165e27e985ea7ec374796dd569d96808b0e8685b..d9f3723d37440784e80a6b2117036c475befebb4 100644
--- a/pkg/compiler/lib/src/kernel/element_map_impl.dart
+++ b/pkg/compiler/lib/src/kernel/element_map_impl.dart
@@ -1692,44 +1692,26 @@ class KernelNativeMemberResolver extends NativeMemberResolverBase {
 
 class JsToFrontendMapImpl extends JsToFrontendMapBase
     implements JsToFrontendMap {
-  final KernelToElementMapBase _frontend;
   final KernelToElementMapBase _backend;
 
-  JsToFrontendMapImpl(this._frontend, this._backend);
+  JsToFrontendMapImpl(this._backend);
 
   LibraryEntity toBackendLibrary(covariant IndexedLibrary library) {
     return _backend._libraryList[library.libraryIndex];
   }
 
-  LibraryEntity toFrontendLibrary(covariant IndexedLibrary library) {
-    return _frontend._libraryList[library.libraryIndex];
-  }
-
   ClassEntity toBackendClass(covariant IndexedClass cls) {
     return _backend._classList[cls.classIndex];
   }
 
-  ClassEntity toFrontendClass(covariant IndexedClass cls) {
-    return _frontend._classList[cls.classIndex];
-  }
-
   MemberEntity toBackendMember(covariant IndexedMember member) {
     return _backend._memberList[member.memberIndex];
   }
 
-  MemberEntity toFrontendMember(covariant IndexedMember member) {
-    return _frontend._memberList[member.memberIndex];
-  }
-
   TypeVariableEntity toBackendTypeVariable(
       covariant IndexedTypeVariable typeVariable) {
     return _backend._typeVariableList[typeVariable.typeVariableIndex];
   }
-
-  TypeVariableEntity toFrontendTypeVariable(
-      covariant IndexedTypeVariable typeVariable) {
-    return _frontend._typeVariableList[typeVariable.typeVariableIndex];
-  }
 }
 
 class JsKernelToElementMap extends KernelToElementMapBase
@@ -1747,12 +1729,9 @@ class JsKernelToElementMap extends KernelToElementMapBase
         ElementCreatorMixin
     implements
         KernelToWorldBuilder {
-  JsToFrontendMap _jsToFrontendMap;
-
   JsKernelToElementMap(DiagnosticReporter reporter, Environment environment,
       KernelToElementMapForImpactImpl _elementMap)
       : super(reporter, environment) {
-    _jsToFrontendMap = new JsToFrontendMapImpl(_elementMap, this);
     _env = _elementMap._env;
     for (int libraryIndex = 0;
         libraryIndex < _elementMap._libraryEnvs.length;
@@ -1827,8 +1806,6 @@ class JsKernelToElementMap extends KernelToElementMapBase
     return true;
   }
 
-  JsToFrontendMap get jsToFrontendMap => _jsToFrontendMap;
-
   @override
   Spannable getSpannable(MemberEntity member, ir.Node node) {
     return _getSpannable(member, node);