Specify the tokenizer for window.open's features argument

This was specified in CSSOM View but the "noopener" feature did
not use the same tokenizer as the legacy features. Fixes #2474.

Also specify the aliases screenx, screeny, innerwidth, innerheight
for left, top, width, and height, respectively. Part of #2464.
Closes w3c/csswg-drafts#1128.

source

@@ -78669,8 +78669,11 @@ callback <dfn>FrameRequestCallback</dfn> = void (<span>DOMHighResTimeStamp</span
    indicating a preference for navigating a new <span>top-level browsing context</span>, then let
    <var>new</var> be true. Otherwise, let it be false.</p></li>
 
-   <li><p>Interpret <var>features</var> <span data-x="dom-open-features">as defined in the CSSOM
-   View specification</span>. <ref spec="CSSOMVIEW"></p></li>
+   <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>Interpret <var>tokenizedFeatures</var> <span data-x="dom-open-features">as defined in the
+   CSSOM View specification</span>. <ref spec="CSSOMVIEW"></p></li>
 
    <li>
 
@@ -78725,10 +78728,9 @@ callback <dfn>FrameRequestCallback</dfn> = void (<span>DOMHighResTimeStamp</span
 
     <ol>
 
-     <li><p>If the result of <span data-x="split a string on commas">splitting <var>features</var>
-     on commas</span> contains the token "<code data-x="">noopener</code>", then <span
-     data-x="disowned its opener">disown <var>target browsing context</var>'s opener</span> and
-     return null.</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 <span data-x="disowned its opener">disown
+     <var>target browsing context</var>'s opener</span> and return null.</p></li>
 
      <li><p>Otherwise, return the <code>WindowProxy</code> object of <var>target browsing
      context</var>.</p></li>
@@ -78739,6 +78741,66 @@ callback <dfn>FrameRequestCallback</dfn> = void (<span>DOMHighResTimeStamp</span
 
   </ol>
 
+  <p>To <dfn data-x="concept-window-open-features-tokenize">tokenize the <var>features</var>
+  argument</dfn>:</p>
+
+  <ol>
+   <li><p>Let <var>tokens</var> be the result of <span data-x="split a string on commas">splitting
+   <var>features</var> on commas</span>.</p></li>
+
+   <li><p>Let <var>map</var> be a new <span>ordered map</span>.</p></li>
+
+   <li>
+    <p>For each <var>token</var> of <var>tokens</var>:</p>
+    <ol>
+     <li><p>Let <var>input</var> be <var>token</var>.
+
+     <li><p>Let <var>position</var> point at the first character of <var>input</var>.</p></li>
+
+     <li><p><span>Skip ASCII whitespace</span>.
+
+     <li><p><span>Collect a sequence of code points</span> that are not <span>ASCII
+     whitespace</span> nor U+003D (=). Let <var>name</var> be the collected characters,
+     <span>converted to ASCII lowercase</span>.</p></li>
+
+     <li><p>Set <var>name</var> to the result of <span>normalizing the feature name</span>
+     <var>name</var>.</p></li>
+
+     <li><p>If <var>tokenizedFeatures</var>[<var>name</var>] <span data-x="map
+     exists">exists</span>, then continue.</p></li>
+
+     <li><p><span>Skip ASCII whitespace</span>.</p></li>
+
+     <li><p>If the character at <var>position</var> is U+003D (=), then advance <var>position</var>
+     by 1.</p></li>
+
+     <li><p>Let <var>value</var> be the empty string.</p></li>
+
+     <li><p>If <var>position</var> is not past the end of <var>input</var>, then <span>collect a
+     sequence of code points</span> that are any characters. Set <var>value</var> to the collected
+     characters.</p></li>
+
+     <li><p>Set <var>tokenizedFeatures</var>[<var>name</var>] to <var>value</var>.</p></li>
+    </ol>
+   </li>
+  </ol>
+
+  <p>For legacy reasons, there are some aliases of some feature names. To <dfn data-x="normalizing
+  the feature name">normalize a feature name</dfn> <var>name</var>, switch on <var>name</var>:</p>
+
+  <dl class="switch">
+   <dt>"<code data-x="">screenx</code>"
+   <dd>Return "<code data-x="">left</code>".
+   <dt>"<code data-x="">screeny</code>"
+   <dd>Return "<code data-x="">top</code>".
+   <dt>"<code data-x="">innerwidth</code>"
+   <dd>Return "<code data-x="">width</code>".
+   <dt>"<code data-x="">innerheight</code>"
+   <dd>Return "<code data-x="">height</code>".
+   <dt>Anything else
+   <dd>Return <var>name</var>.
+  </dl>
+
   <hr>
 
   <p>The <dfn><code data-x="dom-name">name</code></dfn> attribute of the <code>Window</code> object