title: Magento 2 load very slowly after changing less file
body: <p>I'm trying to create new theme. But every time I reload the home page it is going to high CPU loading.</p>
  
  <p>My Settings:<br />
  <strong>New theme has just one file</strong>: /app/design/frontend/Test/default/web/css/source/_extend.less<br />
  <strong>Magento mode</strong>: developer<br />
  <strong>Front-end development workflow</strong>: Server-side less compilation<br />
  <strong>Grunt</strong>: installed and configured.</p>
  
  <p>Activity monitor:</p>
  
  <p><a href="https://i.stack.imgur.com/fq2K8.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fq2K8.png" alt="Mac os activity monitor"></a></p>
  
  <p>Chrome console:</p>
  
  <p><a href="https://i.stack.imgur.com/gKj22.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gKj22.png" alt="enter image description here"></a></p>
  
  <p>And only after <code>php bin/magento setup:static-content:deploy</code> the page is loading fast:</p>
  
  <p><a href="https://i.stack.imgur.com/DQDhL.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DQDhL.png" alt="enter image description here"></a></p>
  
  <p>Do I need to deploy static content every time I change some css style if I develop new theme?</p>
  
  <p>Thanks in advance!</p>