CodePen

HTML

            
              <div id="main">
  <div id="toolbar"></div>
  <textarea resize></textarea>
</div>
            
          
!

CSS

            
              #main {
  background-color: #ddd;
  height: 200px; width: 400px;
  position: relative;
  top: 40px;
}

#toolbar {
  background-color: #444;
  height: 40px; width: 100%;
  position: absolute;
  top: -40px;
}

textarea {
  width: 100%; height: 100%;
  box-sizing: border-box;
}
            
          
!

JS

            
              
            
          
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999px
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