Split KernelToElementMap mixins to match interfaces

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 723 matching lines @@
     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, KernelToElementMapMixin elementMap,
+void checkLibrary(Compiler compiler, KernelToElementMapImpl 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);
       });
@@ skipping 129 matching lines @@
         builder.registerFeature(Feature.THROW_EXPRESSION);
         break;
       default:
         builder.registerFeature(feature);
         break;
     }
   }
   impact.nativeData.forEach(builder.registerNativeData);
   return builder;
 }