recommendation for when add/queue steps should run

Closes #55.

Author: igrigorik

index.html

@@ -855,9 +855,16 @@ <h3>Processing Model</h3>
       </li>
       <li><a href='https://www.w3.org/TR/performance-timeline-2/#dfn-queue-a-performanceentry'>Queue</a> the <a>PerformanceResourceTiming</a> object.
       </li>
-      <li><a data-lt='add a PerformanceResourceTiming entry'>Add</a> the <a>PerformanceResourceTiming</a> object.
+      <li><a data-lt='add a PerformanceResourceTiming entry'>Add</a> the <a>PerformanceResourceTiming</a> object to the <a href='https://www.w3.org/TR/performance-timeline-2/#dfn-performance-entry-buffer'>performance entry buffer</a>.</li>
       </li>
   </ol>
+  <p class="note">
+    This specification does not specify whether steps 20 and 21 should run
+    before or after the <code>load</code> event of the resource. However, where
+    applicable, the user agent is encouraged to run them after the
+    <code>load</code> event of the resource has finished—see
+    <a href="https://github.com/w3c/resource-timing/issues/55#issuecomment-260075811">related discussion</a>.
+  </p>
 </section>
 <section id="monotonic-clock">
 <h3>Monotonic Clock</h3>