Assert that we don't mix K and J elements

pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart

Index: pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
diff --git a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
index a5b537e34f0d5f76cb068460b4ca42673cca8ba2..0b28034cda5a51a76c79c9f731d412207918d485 100644
--- a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
+++ b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
@@ -63,7 +63,7 @@ class KernelAstAdapter extends KernelToElementMapBaseMixin
   KernelAstAdapter(this.kernel, this._backend, this._resolvedAst,
       this._nodeToAst, this._nodeToElement)
       : nativeBehaviorBuilder = new native.ResolverBehaviorBuilder(
-            _backend.compiler, _backend.nativeBasicData) {
+            _backend.compiler, _backend.frontendStrategy.nativeBasicData) {
     KernelJumpTarget.index = 0;
     // TODO(het): Maybe just use all of the kernel maps directly?
     for (FieldElement fieldElement in kernel.fields.keys) {