title: How to programmatically clear PaperInput and have the floating label drop down to the input line
body: <p>I have the following markup:</p>
  
  
  
  <pre class="lang-dart prettyprint-override"><code>&lt;paper-input id="alias-input" floatingLabel label="Person Alias (eg: King, Eldest Son, Mooch, etc.)"&gt;&lt;/paper-input&gt;
  &lt;paper-input id="birth-year-input" floatingLabel label="Birth Year (eg: 1969)" validate="^[12][0-9][0-9][0-9]$"&gt;&lt;/paper-input&gt;
  
  &lt;div center horizontal layout&gt;
    &lt;paper-button id="add-button" on-click="{{addPerson}}" class="add" label="Add Person"&gt;&lt;/paper-button&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>To go along with this markup I have an <em>addButton</em> method which does:</p>
  
  <pre class="lang-dart prettyprint-override"><code>addPerson(_) {
    // Add the person
    // ...
  
    // Clear the inputs
    ($['alias-input'] as PaperInput)..inputValue = ''..commit()..blur();
    ($['birth-year-input'] as PaperInput)..inputValue = ''..commit()..blur();
  }
  </code></pre>
  
  <p>This correctly clears the contents of the inputs, which I want. But I also want the PaperInput help label to drop down onto the line as it is when the control is first loaded. My hope was that the call to <em>blur()</em> would do that. Is there some other call to achieve this?</p>