Use JsStrategy, remove KernelBackendStrategy

tests/compiler/dart2js/kernel/impact_test.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.kernel.impact_test;
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common.dart';
 import 'package:compiler/src/common/names.dart';
 import 'package:compiler/src/common/resolution.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/constants/expressions.dart';
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/elements/entities.dart';
 import 'package:compiler/src/elements/resolution_types.dart';
 import 'package:compiler/src/js_backend/backend.dart';
+import 'package:compiler/src/kernel/element_map.dart';
 import 'package:compiler/src/kernel/element_map_impl.dart';
 import 'package:compiler/src/resolution/registry.dart';
 import 'package:compiler/src/resolution/tree_elements.dart';
 import 'package:compiler/src/ssa/kernel_impact.dart';
 import 'package:compiler/src/serialization/equivalence.dart';
 import 'package:compiler/src/universe/call_structure.dart';
 import 'package:compiler/src/universe/feature.dart';
 import 'package:compiler/src/universe/use.dart';
 import 'package:expect/expect.dart';
 import 'package:kernel/ast.dart' as ir;
@@ skipping 709 matching lines @@
         entryPoint: entryPoint,
         memorySourceFiles: SOURCE,
         options: [
           fullTest ? Flags.analyzeAll : Flags.analyzeOnly,
           Flags.useKernel,
           Flags.enableAssertMessage
         ]);
     compiler.resolution.retainCachesForTesting = true;
     Expect.isTrue(await compiler.run(entryPoint));
     JavaScriptBackend backend = compiler.backend;
-    KernelToElementMapImpl kernelElementMap =
-        new KernelToElementMapImpl(compiler.reporter, compiler.environment);
+    KernelToElementMapForImpact kernelElementMap =
+        new KernelToElementMapForImpactImpl(
+            compiler.reporter, compiler.environment);
     kernelElementMap.addProgram(backend.kernelTask.program);
 
     LibraryElement mainApp =
         compiler.frontendStrategy.elementEnvironment.mainLibrary;
     checkLibrary(compiler, kernelElementMap, mainApp, fullTest: fullTest);
     compiler.libraryLoader.libraries.forEach((LibraryEntity library) {
       if (library == mainApp) return;
       checkLibrary(compiler, kernelElementMap, library, fullTest: fullTest);
     });
   });
 }
 
-void checkLibrary(Compiler compiler, KernelToElementMapImpl elementMap,
+void checkLibrary(Compiler compiler, KernelToElementMapForImpact elementMap,
     LibraryElement library,
     {bool fullTest: false}) {
   library.forEachLocalMember((_element) {
     AstElement element = _element;
     if (element.isClass) {
       ClassElement cls = element;
       cls.forEachLocalMember((_member) {
         AstElement member = _member;
         checkElement(compiler, elementMap, member, fullTest: fullTest);
       });
     } else if (element.isTypedef) {
       // Skip typedefs.
     } else {
       checkElement(compiler, elementMap, element, fullTest: fullTest);
     }
   });
 }
 
-void checkElement(
-    Compiler compiler, KernelToElementMapImpl elementMap, AstElement element,
+void checkElement(Compiler compiler, KernelToElementMapForImpact elementMap,
+    AstElement element,
     {bool fullTest: false}) {
   if (!fullTest && element.library.isPlatformLibrary) {
     return;
   }
   if (element.isConstructor) {
     ConstructorElement constructor = element;
     if (constructor.isRedirectingFactory) {
       // Skip redirecting constructors for now; they might not be supported.
       return;
     }
@@ skipping 109 matching lines @@
         builder.registerFeature(Feature.THROW_EXPRESSION);
         break;
       default:
         builder.registerFeature(feature);
         break;
     }
   }
   impact.nativeData.forEach(builder.registerNativeData);
   return builder;
 }