title: Angular 4 TypeScript, click a button to pop file open dialog
body: <p>Want to open the standard file open dialog when clicking follow button in the .component.html:</p>
  
  <pre><code>&lt;button md-fab md-tooltip="Input"&gt;
      &lt;md-icon class="md-24"&gt;input&lt;/md-icon&gt;
  &lt;/button&gt;
  </code></pre>
  
  <p>seems the common way to open a dialog is to use input tag like this:</p>
  
  <pre><code>&lt;input type=”file”&gt;
  </code></pre>
  
  <p>but it shows extra things on screen. Thinking of do popping up in the .component.ts with a (click) in the :</p>
  
  <pre><code>&lt;button md-fab md-tooltip="Input" (click)="onClick()"&gt;
      &lt;md-icon class="md-24"&gt;input&lt;/md-icon&gt;
  &lt;/button
  </code></pre>
  
  <p>but couldn't find a way to pop up file open dialog in .ts, please help.</p>
  
  <p>@angular/cli: 1.0.1
  node: 7.7.4
  os: win32 x64
  @angular/xxxx: 4.0.3</p>