Support creating elements from IR nodes in JsKernelToElementMap

pkg/compiler/lib/src/js_model/js_strategy.dart

Index: pkg/compiler/lib/src/js_model/js_strategy.dart
diff --git a/pkg/compiler/lib/src/js_model/js_strategy.dart b/pkg/compiler/lib/src/js_model/js_strategy.dart
index 138c6cc3f3496604ecd845ad337e39a3f4591e04..8203349414e19eacc2c629dd9aedfd34e2536606 100644
--- a/pkg/compiler/lib/src/js_model/js_strategy.dart
+++ b/pkg/compiler/lib/src/js_model/js_strategy.dart
@@ -114,6 +114,7 @@ class JsBackendStrategy implements KernelBackendStrategy {
 
     return new JsClosedWorld(
         elementEnvironment: _elementEnvironment,
+        dartTypes: _elementMap.types,
         commonElements: _commonElements,
         constantSystem: const JavaScriptConstantSystem(),
         backendUsage: backendUsage,
@@ -122,8 +123,12 @@ class JsBackendStrategy implements KernelBackendStrategy {
         classHierarchyNodes: classHierarchyNodes,
         classSets: classSets,
         implementedClasses: implementedClasses,
-        // TODO(johnniwinther): Support this.
-        allTypedefs: new ImmutableEmptySet<TypedefElement>());
+        // TODO(johnniwinther): Support these.
+        allTypedefs: new ImmutableEmptySet<TypedefElement>(),
+        resolutionWorldBuilder: null,
+        functionSet: null,
+        mixinUses: null,
+        typesImplementedBySubclasses: null);
   }
 
   @override