anchor.diff:    SsaOptimizerTask optimizer;
     SsaCodeGeneratorTask generator;
     CodeEmitterTask emitter;
  +
  +  List<CompilerTask> get tasks() {
  +    return <CompilerTask>[builder, optimizer, generator, emitter];
  +  }
   
     JavaScriptBackend(Compiler compiler)
         : emitter = new CodeEmitterTask(compiler),
  
positive.code:     native.processNativeClasses(world, emitter, libraries);
    }
  
    void assembleProgram() => emitter.assembleProgram();
  }
  
  class DartBackend extends Backend {
    DartBackend(Compiler compiler) : super(compiler);
  }
  
  class Compiler implements DiagnosticListener {
  
negative.code:     enqueuer = new EnqueueTask(this);
      tasks = [scanner, dietParser, parser, resolver, checker,
               unparseValidator, constantHandler, enqueuer];
      tasks.addAll(backend.tasks);
    }
  
    Universe get codegenWorld() => enqueuer.codegen.universe;
  