anchor.diff:  
     JavaScriptConstantTask constantCompilerTask;
   
  -  JavaScriptionResolutionCallbacks resolutionCallbacks;
  +  JavaScriptResolutionCallbacks resolutionCallbacks;
   
     JavaScriptBackend(Compiler compiler, bool generateSourceMap)
         : namer = determineNamer(compiler),
  
positive.code:     typeVariableHandler = new TypeVariableHandler(this);
      customElementsAnalysis = new CustomElementsAnalysis(this);
      constantCompilerTask = new JavaScriptConstantTask(compiler);
      resolutionCallbacks = new JavaScriptionResolutionCallbacks(this);
    }
  
    ConstantSystem get constantSystem => constants.constantSystem;
  
negative.code:   }
  }
  
  class JavaScriptResolutionCallbacks extends ResolutionCallbacks {
    final JavaScriptBackend backend;
  
    JavaScriptResolutionCallbacks(this.backend);
  
    void registerBackendStaticInvocation(Element element, Registry registry) {
      registry.registerStaticInvocation(backend.registerBackendUse(element));
  