title: woocommerce_before_calculate_totals hook stopped working after update to WC 3.0.1
body: <p>I have updated to WC 3.0.1 from 2.6.14.<br>
  My original code is as follows:</p>
  
  <pre><code>add_action( 'woocommerce_before_calculate_totals', 'add_custom_price' );
  
  function add_custom_price( $cart_object ) {
      $custom_price = 10; // This will be your custome price  
      foreach ( $cart_object-&gt;cart_contents as $key =&gt; $value ) {
          $value['data']-&gt;price = $custom_price;
      }
  }
  </code></pre>
  
  <p>It is no longer updating the price in cart or minicart.</p>