title: Is there any methods to solve "unimplemented pure virtual method"
body: <p>I'm using Emscripten to build my C++ source code to JavaScript, and I met some problem about how to write correct interface description in WebIDL file.</p>
  <p>C++ code example:</p>
  <pre class="lang-cpp prettyprint-override"><code>class Base
  {
  public:
      virtual bool is_true() const = 0;
      virtual int get_count() const = 0;
  }
  
  class Child: public Base
  {
  public:
      virtual bool is_true() const
      {
          return true;
      }
      virtual int get_count() const
      {
          return 10;
      }
  }
  </code></pre>
  <p>But how to write WebIDL especially about <code>class Base</code>?</p>
  <pre><code>interface Base{
      // ?
  };
  </code></pre>