Relativize and coarsen timestamps in "update the rendering"

When passing them to web animations, requestAnimationFrame(), and IntersectionObserver.

Closes #7931.

source

@@ -3370,6 +3370,8 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
     <p><cite>High Resolution Time</cite> provides the <dfn
     data-x-href="https://w3c.github.io/hr-time/#dfn-current-high-resolution-time">current high
     resolution time</dfn>, the <dfn
+    data-x-href="https://w3c.github.io/hr-time/#dfn-relative-high-resolution-time">relative high
+    resolution time</dfn>, the <dfn
     data-x-href="https://w3c.github.io/hr-time/#dfn-unsafe-shared-current-time">unsafe shared
     current time</dfn>, the <dfn
     data-x-href="https://w3c.github.io/hr-time/#dfn-shared-monotonic-clock">shared monotonic clock</dfn>,
@@ -106946,7 +106948,9 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
 
      <li><p>For each <span>fully active</span> <code>Document</code> in <var>docs</var>,
      <span>update animations and send events</span> for that <code>Document</code>, passing in
-     <var>now</var> as the timestamp. <ref>WEBANIMATIONS</ref></p></li>
+     <span>relative high resolution time</span> given <var>now</var> and that
+     <code>Document</code>'s <span>relevant global object</span> as the timestamp.
+     <ref>WEBANIMATIONS</ref></p></li>
 
      <li><p>For each <span>fully active</span> <code>Document</code> in <var>docs</var>, <span>run
      the fullscreen steps</span> for that <code>Document</code>. <ref>FULLSCREEN</ref></p></li>
@@ -106988,8 +106992,9 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
      </li>
 
      <li><p>For each <span>fully active</span> <code>Document</code> in <var>docs</var>, <span>run
-     the animation frame callbacks</span> for that <code>Document</code>, passing in <var>now</var>
-     as the timestamp.</p></li>
+     the animation frame callbacks</span> for that <code>Document</code>, passing in the
+     <span>relative high resolution time</span> given <var>now</var> and that
+     <code>Document</code>'s <span>relevant global object</span> as the timestamp.</p></li>
 
      <li>
       <p>For each <span>fully active</span> <code>Document</code> <var>doc</var> in
@@ -107080,9 +107085,11 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
      <span>perform pending transition operations</span> for that <code>Document</code>.
      <ref>CSSVIEWTRANSITIONS</ref></p></li>
 
-      <li><p>For each <span>fully active</span> <code>Document</code> in <var>docs</var>, <span>run
+     <li><p>For each <span>fully active</span> <code>Document</code> in <var>docs</var>, <span>run
      the update intersection observations steps</span> for that <code>Document</code>, passing in
-     <var>now</var> as the timestamp. <ref>INTERSECTIONOBSERVER</ref></p></li>
+     the <span>relative high resolution time</span> given <var>now</var> and that
+     <code>Document</code>'s <span>relevant global object</span> as the timestamp.
+     <ref>INTERSECTIONOBSERVER</ref></p></li>
 
      <li><p>Invoke the <span>mark paint timing</span> algorithm for each <code>Document</code>
      object in <var>docs</var>.</p></li>