title: Declaring protected attribute in interface
body: <p>Is it possible to declare protected attributes in TypeScript interfaces?</p>
  
  <p>For example:</p>
  
  <pre><code>interface IsDrawable {
    // protected // &lt;- seems to be unsupported
    cssClass: string;
  }
  
  class SomeClass implements IsDrawable {
    protected // &lt;- errors
    cssClass: string;
  }
  </code></pre>
  
  <p>SomeClass errors with `Class 'SomeClass' incorrectly implements interface 'IsDrawable'.  Property 'cssClass' is protected in type 'SomeClass' but  public in type 'IsDrawable'.</p>