.form-inline input width in Bootstrap 3

The question is similar to this, but mine is about the form-inline. It is easier to see the rendered page at Bootply. So, how can I make the pink element fill the border-blue one?

HTML:

<div class="container">
  <div class="row border-gray">

    <div class="col-md-9 border-gray">
      <h1>Bootstrap starter template</h1>
      <p>Use this document as a way to quick start any new project.<br> All you get is this message and a barebones HTML document.</p>
    </div>

    <div class="col-md-3 border-gray">
      <aside>
        <form class="form-inline border-blue" role="form">
          <div class="form-group pink">
            <div class="col-md-12">
              <label class="sr-only" for="pattern">"Search"</label>
              <input type="text" class="form-control" placeholder="Search" name="pattern">
            </div>
          </div>
        </form>
      </aside>
    </div>

  </div>
</div> <!-- /container -->