anchor.diff:  :marked
     Had the user clicked the *Update Hero* button, the log would show another `OnChanges` and two more triplets of
     `DoCheck`, `AfterContentChecked` and `AfterViewChecked`.
  -  Clearly these three hooks fire a *often*. Keep the logic in these hooks as lean as possible!
  +  Clearly these three hooks fire *often*. Keep the logic in these hooks as lean as possible!
   
     The next examples focus on hook details.
   
  
positive.code: :marked
  .l-sub-section
    :marked
      The tell-tale signs of *content projection* are (a) HTML between component element tags
      and (b) the presence of `<ng-content>` tags in the component's template.
  :marked
    ### AfterContent hooks
    *AfterContent* hooks are similar to the *AfterView* hooks. 
    The key difference is in the child component
  
    * The *AfterView* hooks concern `ViewChildren`, the child components whose element tags
    appear *within* the component's template.
  
negative.code: a#other-lifecycle-hooks
  .l-main-section
  :marked
    ## Other Angular lifecycle hooks
  
    Other Angular sub-systems may have their own lifecycle hooks apart from these component hooks.
  
  