Compute ResolutionImpact directly from kernel, part 1 of ?

pkg/compiler/lib/src/js_backend/backend.dart

 // Copyright (c) 2012, 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 js_backend.backend;
 
 import 'dart:async' show Future;
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
 
@@ skipping 617 matching lines @@
 
   CoreTypes get coreTypes => compiler.coreTypes;
 
   Resolution get resolution => compiler.resolution;
 
   /// Returns constant environment for the JavaScript interpretation of the
   /// constants.
   JavaScriptConstantCompiler get constants {
     return constantCompilerTask.jsConstantCompiler;
   }
-  
+
   @override
   bool isDefaultNoSuchMethod(MethodElement element) {
     return noSuchMethodRegistry.isDefaultNoSuchMethodImplementation(element);
   }
 
   MethodElement resolveExternalFunction(MethodElement element) {
     if (isForeign(element)) {
       return element;
     }
     if (isJsInterop(element)) {
@@ skipping 2557 matching lines @@
 
   @override
   void onImpactUsed(ImpactUseCase impactUse) {
     if (impactUse == DeferredLoadTask.IMPACT_USE && !supportSerialization) {
       // TODO(johnniwinther): Allow emptying when serialization has been
       // performed.
       resolution.emptyCache();
     }
   }
 }