CV: Add content attribute handling + test

This patch adds a content attribute parsing and a wpt test for
contentvisibilityautostatechange event

[email protected]

Change-Id: Iae610a794477d3ca0b346b752b489cd101399fcc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5570779
Commit-Queue: Vladimir Levin <[email protected]>
Reviewed-by: Khushal Sagar <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1305905}

css/css-contain/content-visibility/content-visibility-auto-state-changed.html

@@ -21,7 +21,18 @@
 .auto { content-visibility: auto; }
 </style>
 
+<script>
+let contentattrfired = false;
+
+function contentattrDidFire() {
+  contentattrfired = true;
+}
+
+</script>
+
 <div id=upper></div>
+<div id=attrtest></div>
+<div id=contentattrtest oncontentvisibilityautostatechange="contentattrDidFire()" class=auto></div>
 <div class=spacer></div>
 <div id=middle></div>
 <div class=spacer></div>
@@ -40,6 +51,18 @@
   upper.classList.add("auto");
 }), "ContentVisibilityAutoStateChange fires when relevant element gains `content-visibility:auto`");
 
+promise_test(t => new Promise(async (resolve, reject) => {
+  let shouldSkip = false;
+  const listener = (e) => {
+    if (!e.skipped)
+      resolve();
+  };
+
+  attrtest.oncontentvisibilityautostatechange = listener;
+  t.add_cleanup(() => { attrtest.oncontentvisibilityautostatechange = () => {} });
+  attrtest.classList.add("auto");
+}), "ContentVisibilityAutoStateChange fires when relevant element gains `content-visibility:auto` (oncontentvisibilityautostatechange syntax)");
+
 promise_test(t => new Promise(async (resolve, reject) => {
   let shouldSkip = false;
   const listener = (e) => {
@@ -54,6 +77,14 @@
   lower.classList.add("auto");
 }), "ContentVisibilityAutoStateChange fires when not relevant element gains `content-visibility:auto`");
 
+async_test(t => {
+  requestAnimationFrame(() => requestAnimationFrame(() => {
+    t.step(() => assert_true(contentattrfired, "contentattrfired"));
+    t.done();
+  }));
+
+}, "ContentVisibilityAutoStateChange content attribute test");
+
 promise_test(t => new Promise(async (resolve, reject) => {
   await new Promise((waited, _) => {
     requestAnimationFrame(() => requestAnimationFrame(waited));