title: input placeholder issue on IE11
body: <p>I am new to <code>angular 2</code> and <code>angular 4</code> . I have just converted my application from 2 to 4. So, here I am facing an issue , <strong>On IE11, when receives focus, placeholder is removed and form control is set to dirty and pristine is set to false. On chrome / FF, this issue never occurs.</strong></p>
  
  <p>My Html is like -</p>
  
  <pre><code>    &lt;input type="text" class="form-control" id="processName" 
                           [(ngModel)]="process.displayName" [disabled]="isProcessLoading"
                           #processName="ngModel" maxLength="64" pattern="^.*\S.*" name="processName"
   placeholder="{{'PROCESS-FORM.name-placeholder' | translate}}" required
                           placeholderRequired [inputBinding]="processName"/&gt;
  </code></pre>
  
  <p>I am not able to understand why this is happening ? Thanks in the advance .</p>