[css-pseudo-4] Add @delan's tests w3c#6316 w3c#6603

Author: fantasai

css-pseudo-4/Overview.bs

@@ -793,6 +793,15 @@ Paired Defaults</h4>
     </pre>
   </div>
 
+  <wpt>
+  css/css-pseudo/highlight-paired-cascade-001.html
+  css/css-pseudo/highlight-paired-cascade-002.html
+  css/css-pseudo/highlight-paired-cascade-003.html
+  css/css-pseudo/highlight-paired-cascade-004.html
+  css/css-pseudo/highlight-paired-cascade-005.html
+  css/css-pseudo/highlight-paired-cascade-006.html
+  </wpt>
+
 <h3 id=highlight-bounds>
 Area of a Highlight</h3>
 
@@ -956,6 +965,7 @@ Backgrounds</h4>
   css/css-pseudo/selection-overlay-and-spelling-001.html
   css/css-pseudo/highlight-z-index-001.html
   css/css-pseudo/highlight-z-index-002.html
+  css/css-pseudo/selection-background-painting-order.html
   </wpt>
 
 <h4 id="highlight-shadows">
@@ -1056,6 +1066,12 @@ Text and Text Decorations</h4>
   propagate to [=out-of-flow|out-of-flow elements=] and [=inline blocks=],
   with thickness and position varying between descendants.
 
+  <wpt>
+  css/css-pseudo/selection-originating-underline-order.html
+  css/css-pseudo/selection-originating-decoration-color.html
+  css/css-pseudo/selection-originating-strikethrough-order.html
+  </wpt>
+
 <h4 id="highlight-replaced">
 Replaced Elements</h4>