title: Angular Material progress spinner size in flex layout
body: <p>I have a <code>fxFlex="row"</code> inside of which there's a <code>button</code> and a <code>mat-spinner</code>. I want the <code>mat-spinner</code>'s size to be the same as the <code>button</code> (i.e., to fit nicely in the row).</p>
  
  <p>The current behaviour is that the progress spinner is too big. Code:</p>
  
  <pre><code>&lt;div fxLayout="row"&gt;
    &lt;button fxFlexAlign="start" mat-stroked-button&gt;Do something&lt;/button&gt;
    &lt;mat-spinner *ngIf="loading"&gt;&lt;/mat-spinner&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>I know there's a <code>diameter</code> property but I'm not sure which value I should set it with (if that's the only solution). I'd prefer to make the solution as dynamic as possible.</p>