title: How to set indent size in ACE editor
body: <p>I created an ACE editor instance using the following code:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var editor = ace.edit("editor");
  editor.setTheme("ace/theme/monokai");
  editor.getSession().setMode("ace/mode/javascript");</code></pre>
  <pre class="snippet-code-css lang-css prettyprint-override"><code>#editor {
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/ace/1.1.9/ace.js"&gt;&lt;/script&gt;
  
  &lt;div id="editor"&gt;function foo (x) {
      return 2 * x;
  }
  
  function bar (y) {
      return foo(y) / 2;
  }
  
  console.log(bar(2) + foo(3));&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>I want to control the indent size (especially when pressing the <kbd>tab</kbd> key).  How can I do that?</p>
  
  <p>I searched in the API reference but I couldn't find the solution...</p>