Specify parsing of 'noopener' feature in window.open

Specify parsing of 'noopener' feature in window.open so that noopener is only set to true
if the value is either:
- The empty string.
- The string "yes".
- The value is not 0 or an error when parsed as an integer.

Fixes whatwg#2600.

source

@@ -78318,13 +78318,17 @@ interface <dfn data-export="" data-dfn-type="interface">Window</dfn> : <span>Eve
    <li><p>Let <var>tokenizedFeatures</var> be the result of <span
    data-x="concept-window-open-features-tokenize">tokenizing</span> <var>features</var>.</p></li>
 
-   <li><p>Let <var>noopener</var> be true if <var>tokenizedFeatures</var> <span data-x="map
-   exists">contains</span> an entry with the key "<code data-x="">noopener</code>"</p></li>
+   <li><p>Let <var>noopener</var> be false.</p></li>
+
+   <li><p>If <var>tokenizedFeatures</var> <span data-x="map exists">contains</span> an entry with the
+   key "<code data-x="">noopener</code>", then set <var>noopener</var> to the result of <span
+   data-x="concept-window-open-features-parse-boolean">parsing <var>tokenizedFeatures["noopener"]</var>
+   as a boolean feature</span>.</p></li>
 
    <li>
     <p>Let <var>target browsing context</var> and <var>new</var> be the result of applying <span>the
     rules for choosing a browsing context</span> given <var>target</var>, <var>source browsing
-    context</var>, and <var>noopener</var>.
+    context</var>, and <var>noopener</var>.</p>
 
     <p class="example">If there is a user agent that supports control-clicking a link to open it in
     a new tab, and the user control-clicks on an element whose <code
@@ -78477,6 +78481,23 @@ interface <dfn data-export="" data-dfn-type="interface">Window</dfn> : <span>Eve
    <dd>Return <var>name</var>.
   </dl>
 
+  <p>To <dfn data-x="concept-window-open-features-parse-boolean">parse a boolean feature</dfn> given a
+  string <var>value</var>:</p>
+
+  <ol>
+   <li><p>If <var>value</var> is the empty string, then return true.</p></li>
+
+   <li><p>If <var>value</var> is a case-sensitive match for <code data-x="">yes</code>, then return
+   true.</p></li>
+
+   <li><p>Let <var>parsed</var> be the result of <span data-x="rules for parsing integers">parsing
+   <var>value</var> as an integer</span>.</p></li>
+
+   <li><p>If <var>parsed</var> is an error, then set it to 0."</p></li>
+
+   <li><p>If <var>parsed</var> is 0, then return false, otherwise return true.</p></li>
+  </ol>
+
   <hr>
 
   <p>The <dfn><code data-x="dom-name">name</code></dfn> attribute of the <code>Window</code> object