check and consume user activation

Author: marcoscaceres

index.html

@@ -574,7 +574,12 @@ <h3>
         The <dfn>subscribe()</dfn> method when invoked MUST run the following steps:
       </p>
       <ol class="algorithm">
-        <li>Let |promise| be [=a new promise=].
+        <li>If the [=relevant global object=] of [=this=] does not have [=transient activation=],
+        return [=a promise rejected with=] with a {{"NotAllowedError"}} {{DOMException}}.
+        </li>
+        <li>[=Consume user activation=] of [=this=]'s [=relevant global object=].
+        </li>
+        <li>Let |promise| be <a>a new promise</a>.
         </li>
         <li>Let |global| be [=this=]' [=relevant global object=].
         </li>