Split implementation of KernelToElementMapImpl

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

Index: pkg/compiler/lib/src/kernel/kernel_strategy.dart
diff --git a/pkg/compiler/lib/src/kernel/kernel_strategy.dart b/pkg/compiler/lib/src/kernel/kernel_strategy.dart
index 256cfa9d5866166b47f8fba90f4fd24497613137..805b0fe0374c69ee6b7cb52d5c742bbd5d0cc076 100644
--- a/pkg/compiler/lib/src/kernel/kernel_strategy.dart
+++ b/pkg/compiler/lib/src/kernel/kernel_strategy.dart
@@ -34,17 +34,20 @@ import '../universe/world_builder.dart';
 import '../universe/world_impact.dart';
 import '../world.dart';
 import 'element_map_impl.dart';
+import 'kernel_backend_strategy.dart';
 
 /// Front end strategy that loads '.dill' files and builds a resolved element
 /// model from kernel IR nodes.
 class KernelFrontEndStrategy implements FrontendStrategy {
-  KernelToElementMapImpl elementMap;
+  KernelToElementMapForImpactImpl elementMap;
 
   KernelAnnotationProcessor _annotationProcesser;
 
   KernelFrontEndStrategy(
       DiagnosticReporter reporter, env.Environment environment)
-      : elementMap = new KernelToElementMapImpl(reporter, environment);
+      : elementMap = useJsStrategyForTesting
+            ? new KernelToElementMapForImpactImpl2(reporter, environment)
+            : new KernelToElementMapImpl(reporter, environment);
 
   @override
   LibraryLoaderTask createLibraryLoader(
@@ -135,7 +138,7 @@ class KernelFrontEndStrategy implements FrontendStrategy {
 }
 
 class KernelWorkItemBuilder implements WorkItemBuilder {
-  final KernelToElementMapImpl _elementMap;
+  final KernelToElementMapForImpactImpl _elementMap;
   final ImpactTransformer _impactTransformer;
   final NativeMemberResolver _nativeMemberResolver;
 
@@ -152,7 +155,7 @@ class KernelWorkItemBuilder implements WorkItemBuilder {
 }
 
 class KernelWorkItem implements ResolutionWorkItem {
-  final KernelToElementMapImpl _elementMap;
+  final KernelToElementMapForImpactImpl _elementMap;
   final ImpactTransformer _impactTransformer;
   final NativeMemberResolver _nativeMemberResolver;
   final MemberEntity element;