title: angular material doesn't show error message when add attribute dinamically
body: <p>My directive add some attributes dinamically. One these attributes is the "required".</p>
  
  <pre><code>angular.module('MyApp',['ngMaterial', 'ngMessages'])
      .controller('AppCtrl', function($scope) {})
      .directive("stPattern", ['$compile', stPattern]);
  
  function stPattern($compile) {
      return {
          restrict: 'A',
          link: function ($scope, element, attrs, ngModel) {
              $timeout(function() {
                  element
                      .attr("ng-pattern", /^123$/)
                      .attr("required", "required");
  
                  element.removeAttr("st-pattern"); //because compile loop
  
                  $compile(element)($scope);
              }, 2000);
          }
      };
  }
  </code></pre>
  
  <p>In my view I create a form with a input with error messages:</p>
  
  <pre><code>&lt;form name="findForm"&gt;
      &lt;md-input-container&gt;
          &lt;label&gt;CA ID&lt;/label&gt;
          &lt;input type="text" name="findByCaId"
                 ng-model="findByCaId"
                 ng-focus="$event.target.select()"
                 st-pattern=""&gt;
  
          &lt;div ng-messages="findForm.findByCaId.$error"&gt;
              &lt;div ng-message="required"&gt;Campo obrigatório.&lt;/div&gt;
              &lt;div ng-message="pattern"&gt;Valor inválido para o campo CA ID.&lt;/div&gt;
          &lt;/div&gt;
      &lt;/md-input-container&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>When I run the app, the verify happens well but the messages doesn't shows!
  When I inspect the render code on browser with devtools I can see the message div was create well.</p>
  
  <p>I noticed that when the message appears some CSS attributes are applied to the message:</p>
  
  <pre><code>style="opacity: 1; margin-top: 0px;"
  </code></pre>
  
  <p>Another thing i noticed is the asterisk on label which was should have on it.</p>
  
  <p>That behavior is correct? Is a bug?</p>
  
  <p><strong>###UPDATE###</strong></p>
  
  <p>I added the $ timeout to keep the code similar to my problem scenario.</p>
  
  <p><a href="http://codepen.io/rafaeldev/pen/wJgaZV?editors=1010" rel="nofollow noreferrer">I create a fiddle to example.</a></p>
  
  <p>Thanks!</p>