Use JsStrategy, remove KernelBackendStrategy

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

 // Copyright (c) 2017, 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.
 
 part of dart2js.kernel.element_map;
 
 class KernelNoSuchMethodResolver implements NoSuchMethodResolver {
-  final KernelToElementMapForImpactImpl2 elementMap;
+  final KernelToElementMapForImpactImpl elementMap;
 
   KernelNoSuchMethodResolver(this.elementMap);
 
   ElementEnvironment get _elementEnvironment => elementMap.elementEnvironment;
 
   CommonElements get _commonElements => elementMap.commonElements;
 
   @override
   bool hasForwardingSyntax(KFunction method) {
     ir.Procedure node = elementMap._lookupProcedure(method);
@@ skipping 42 matching lines @@
       expr = body.expression;
     }
     return expr is ir.Throw;
   }
 
   @override
   FunctionEntity getSuperNoSuchMethod(FunctionEntity method) {
     return elementMap.getSuperNoSuchMethod(method.enclosingClass);
   }
 }