anchor.diff:  
     ### Registering providers in an NgModule
     
  -  在NgModule中注册提供商。
  +  ### 在NgModule中注册提供商。
     
     Here's our AppModule where we register a `Logger`, an `UserService`, and an `APP_CONFIG` provider.
     
  
positive.code:   We're likely to need the same logger service everywhere in our application,
    so we put it in the project's `#{_appDir}` folder, and
    we register it in the `providers` #{_array} of the metadata for our application module, `AppModule`.
  
  +makeExcerpt('app/providers.component.ts','providers-logger','app/app.component.ts (excerpt)')
  
  
negative.code: :marked
    ### The *Provider* class !{__andProvideFn}
  
    ### *Provider*类和*provide*对象常量
  :marked
    We wrote the `providers` #{_array} like this:
  
  