Отсутствующие стрелки сверху и снизу пользовательской дорожки полосы прокрутки

Question

Я работаю над кодом ниже.Почему мне не хватает стрелок в верхней и нижней части пользовательского трекера полосы прокрутки, чтобы они выглядели как

div{
max-width:150px;
max-height:200px;
 overflow-y: scroll;
  overflow-x: hidden;
}
div::-webkit-scrollbar {
  width: 1em;
}

div::-webkit-scrollbar-track {
  -webkit-box-shadow: inset 0 0 2px rgba(0,0,0,0.3);
  }
  
div::-webkit-scrollbar-thumb {
  background-color: darkgrey;
  outline: 1px solid slategrey;
}

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Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
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Answer 1

для пользовательского трекера полосы прокрутки необходимо добавить псевдоэлемент стиля ::-webkit-scrollbar-button. как это.

div{
max-width:150px;
max-height:200px;
 overflow-y: scroll;
  overflow-x: hidden;
}
div::-webkit-scrollbar {
  width: 1em;
}

div::-webkit-scrollbar-track {
  -webkit-box-shadow: inset 0 0 2px rgba(0,0,0,0.3);
  }
  
div::-webkit-scrollbar-thumb {
  background-color: darkgrey;
  outline: 1px solid slategrey;
}

::-webkit-scrollbar-button {
    background-color: red;
    background-size: 10px 10px;
    background-repeat: no-repeat;
    background-position: center center;
    height: 16px;
    width: 1em;
    -webkit-box-shadow: inset 1px 1px 2px rgba(0,0,0,0.2);
}

::-webkit-scrollbar-button:horizontal:increment {
    background-image: url(https://dl.dropboxusercontent.com/u/55165267/icon2.png);
}

::-webkit-scrollbar-button:end:increment {
    background-image: url(data:image/svg+xml;utf8;base64,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);
}
 

::-webkit-scrollbar-button:start:decrement {
   background-image: url(data:image/svg+xml;utf8;base64,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)
}

<div>

Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
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