update steps to handle re-entracy

Author: ashishkum-ms

index.html

@@ -705,13 +705,13 @@ <h3>Extensions to the HTMLElement interface</h3>
                                 [=active EditContext=], then run the steps to [=deactivate an EditContext=]
                                 with |oldEditContext|.
                             </li>
-                            <li>If |editContext| is not null, then set |editContext|'s <a>associated element</a> to [=this=].
-                            <li>If |oldEditContext| is not null, then:
-                                <ol>
-                                    <li>[=Assert=]: |oldEditContext|'s <a>associated element</a> is equal to [=this=].</li>
-                                    <li>Set |oldEditContext|'s <a>associated element</a> to null.</li>
-                                </ol>
+                            <li>If |oldEditContext| is not null and |oldEditContext|'s <a>associated element</a> is not equal to [=this=], then terminate these steps.</li>
+                            <li>
+                                If |editContext| is not null, |editContext|'s <a>associated element</a> is not null and |editContext|'s <a>associated element</a>
+                                is not equal to [=this=], then [=exception/throw=] a {{"NotSupportedError"}} {{DOMException}}.
                             </li>
+                            <li>If |oldEditContext| is not null, set |oldEditContext|'s <a>associated element</a> to null.</li>
+                            <li>If |editContext| is not null, then set |editContext|'s <a>associated element</a> to [=this=].
                             <li>Set [=this=]'s internal [[\EditContext]] slot to be |editContext|.</li>
                         </ol>
                     </div><!-- algorithm -->