title: Google MDL: drawer icon not centered
body: <p>I'm trying the <a href="http://www.getmdl.io/components/index.html#layout-section/layout" rel="noreferrer">fixed tab example</a> from the Google MDL documentation. Here is my code:</p>
  
  <p><strong>CODE</strong></p>
  
  <pre><code>&lt;!-- Simple header with fixed tabs. --&gt;
      &lt;div class="mdl-layout mdl-js-layout mdl-layout--fixed-header mdl-layout--fixed-tabs"&gt;
        &lt;header class="mdl-layout__header"&gt;
          &lt;div class="mdl-layout__header-row"&gt;
            &lt;!-- Title --&gt;
            &lt;span class="mdl-layout-title"&gt;Title&lt;/span&gt;
          &lt;/div&gt;
          &lt;!-- Tabs --&gt;
          &lt;div class="mdl-layout__tab-bar mdl-js-ripple-effect"&gt;
            &lt;a href="#fixed-tab-1" class="mdl-layout__tab is-active"&gt;Tab 1&lt;/a&gt;
            &lt;a href="#fixed-tab-2" class="mdl-layout__tab"&gt;Tab 2&lt;/a&gt;
            &lt;a href="#fixed-tab-3" class="mdl-layout__tab"&gt;Tab 3&lt;/a&gt;
          &lt;/div&gt;
        &lt;/header&gt;
        &lt;div class="mdl-layout__drawer"&gt;
          &lt;span class="mdl-layout__title"&gt;Title&lt;/span&gt;
        &lt;/div&gt;
        &lt;main class="mdl-layout__content"&gt;
          &lt;section class="mdl-layout__tab-panel is-active" id="fixed-tab-1"&gt;
            &lt;div class="page-content"&gt;&lt;!-- Your content goes here --&gt;&lt;/div&gt;
          &lt;/section&gt;
          &lt;section class="mdl-layout__tab-panel" id="fixed-tab-2"&gt;
            &lt;div class="page-content"&gt;&lt;!-- Your content goes here --&gt;&lt;/div&gt;
          &lt;/section&gt;
          &lt;section class="mdl-layout__tab-panel" id="fixed-tab-3"&gt;
            &lt;div class="page-content"&gt;&lt;!-- Your content goes here --&gt;&lt;/div&gt;
          &lt;/section&gt;
        &lt;/main&gt;
      &lt;/div&gt;
  </code></pre>
  
  <p><strong>OUTPUT</strong></p>
  
  <p><a href="https://i.stack.imgur.com/it7gO.png" rel="noreferrer"><img src="https://i.stack.imgur.com/it7gO.png" alt="Fixed Tabs"></a></p>
  
  <p>The problem is my drawer icon position is wrong!  It is aligned to the top instead of center. What is wrong here?</p>