From 6bf0a5cb5034a7e684dcc3500e841785237ce2dd Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 7 Apr 2024 19:32:43 +0200
Subject: Adding upstream version 1:115.7.0.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 .../paint-timing/fcp-only/buffered-flag.window.js  | 24 ++++++++++
 .../paint-timing/fcp-only/fcp-background-size.html | 38 +++++++++++++++
 .../paint-timing/fcp-only/fcp-bg-image-set.html    | 36 ++++++++++++++
 .../fcp-only/fcp-bg-image-two-steps.html           | 44 +++++++++++++++++
 .../paint-timing/fcp-only/fcp-canvas-context.html  | 24 ++++++++++
 .../fcp-only/fcp-document-opacity-image.html       | 49 +++++++++++++++++++
 .../fcp-only/fcp-document-opacity-text.html        | 39 +++++++++++++++
 .../fcp-ensure-update-the-rendering-step.html      | 55 ++++++++++++++++++++++
 .../tests/paint-timing/fcp-only/fcp-gradient.html  | 27 +++++++++++
 .../tests/paint-timing/fcp-only/fcp-iframe.html    | 27 +++++++++++
 .../fcp-only/fcp-ignore-from-subframe.html         | 27 +++++++++++
 .../fcp-invisible-3d-rotate-descendant.html        | 39 +++++++++++++++
 .../fcp-only/fcp-invisible-3d-rotate.html          | 29 ++++++++++++
 .../fcp-only/fcp-invisible-scale-transition.html   | 30 ++++++++++++
 .../paint-timing/fcp-only/fcp-invisible-scale.html | 40 ++++++++++++++++
 .../paint-timing/fcp-only/fcp-invisible-text.html  | 30 ++++++++++++
 .../fcp-only/fcp-opacity-descendant.html           | 46 ++++++++++++++++++
 .../tests/paint-timing/fcp-only/fcp-opacity.html   | 40 ++++++++++++++++
 .../fcp-only/fcp-out-of-bounds-translate.html      | 30 ++++++++++++
 .../paint-timing/fcp-only/fcp-out-of-bounds.html   | 39 +++++++++++++++
 .../fcp-only/fcp-pseudo-element-display.html       | 32 +++++++++++++
 .../fcp-only/fcp-pseudo-element-image.html         | 38 +++++++++++++++
 .../fcp-only/fcp-pseudo-element-opacity.html       | 32 +++++++++++++
 .../fcp-only/fcp-pseudo-element-text.html          | 28 +++++++++++
 .../fcp-only/fcp-pseudo-element-visibility.html    | 32 +++++++++++++
 .../tests/paint-timing/fcp-only/fcp-svg.html       | 40 ++++++++++++++++
 .../paint-timing/fcp-only/fcp-text-input.html      | 24 ++++++++++
 .../fcp-only/fcp-typographic-pseudo.html           | 32 +++++++++++++
 .../paint-timing/fcp-only/fcp-video-frame.html     | 27 +++++++++++
 .../paint-timing/fcp-only/fcp-video-poster.html    | 28 +++++++++++
 .../paint-timing/fcp-only/fcp-whitespace.html      | 45 ++++++++++++++++++
 .../tests/paint-timing/fcp-only/fcp-with-rtl.html  | 31 ++++++++++++
 .../tests/paint-timing/fcp-only/svg-in-iframe.html | 14 ++++++
 33 files changed, 1116 insertions(+)
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/buffered-flag.window.js
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-background-size.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-bg-image-set.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-bg-image-two-steps.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-canvas-context.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-image.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-text.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-ensure-update-the-rendering-step.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-gradient.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-iframe.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-ignore-from-subframe.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-3d-rotate-descendant.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-3d-rotate.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-scale-transition.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-scale.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-text.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-opacity-descendant.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-opacity.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-out-of-bounds-translate.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-out-of-bounds.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-display.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-image.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-opacity.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-text.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-visibility.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-svg.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-text-input.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-typographic-pseudo.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-video-frame.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-video-poster.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-whitespace.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-with-rtl.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/svg-in-iframe.html

(limited to 'testing/web-platform/tests/paint-timing/fcp-only')

diff --git a/testing/web-platform/tests/paint-timing/fcp-only/buffered-flag.window.js b/testing/web-platform/tests/paint-timing/fcp-only/buffered-flag.window.js
new file mode 100644
index 0000000000..5910b6881f
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/buffered-flag.window.js
@@ -0,0 +1,24 @@
+setup({"hide_test_state": true});
+async_test(t => {
+  assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+  // First observer creates a second one in the callback to ensure the entry has been dispatched
+  // by the time the second observer begins observing.
+  new PerformanceObserver(entries => {
+    const entry_seen = entries.getEntriesByName('first-contentful-paint').length > 0;
+    // Abort if we have not yet received the entry.
+    if (!entry_seen)
+      return;
+
+    // Second observer requires 'buffered: true' to see the entry.
+    new PerformanceObserver(t.step_func_done(list => {
+        const fcp = list.getEntriesByName('first-contentful-paint');
+        assert_equals(fcp.length, 1, 'Should have an fcp entry');
+        const entry = fcp[0];
+        assert_equals(entry.entryType, 'paint');
+      })).observe({'type': 'paint', buffered: true});
+  }).observe({'entryTypes': ['paint']});
+  // Trigger the first contentful paint entry.
+  const img = document.createElement("img");
+  img.src = "../resources/circles.png";
+  document.body.appendChild(img);
+}, "PerformanceObserver with buffered flag sees previous FCP entry.");
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-background-size.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-background-size.html
new file mode 100644
index 0000000000..25fe986bde
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-background-size.html
@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to background size</title>
+<style>
+    #main {
+        position: relative;
+        width: 100px;
+        height: 100px;
+        background-image: url(../resources/circles.png);
+        background-size: 0 0;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful {
+        background-size: 100% 100%;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main"></div>
+<script>
+    // Load the image into memory first to make sure it's decoded.
+    function load_image() {
+      const img = document.createElement("img");
+      img.src = "../resources/circles.png";
+
+      return new Promise(resolve => {
+        img.onload = async () => resolve();
+      });
+    }
+
+    test_fcp("First contentful paint fires due to background size.", load_image);
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-bg-image-set.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-bg-image-set.html
new file mode 100644
index 0000000000..443cef630b
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-bg-image-set.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to background image in image-set</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful {
+        background-image: -webkit-image-set(url(../resources/circles.png) 1x);
+        background-image: image-set(url(../resources/circles.png) 1x);
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main"></div>
+<script>
+    // Load the image into memory first to make sure it's decoded.
+    function load_image() {
+      const img = document.createElement("img");
+      img.src = "../resources/circles.png";
+
+      return new Promise(resolve => {
+        img.onload = async () => resolve();
+      });
+    }
+
+    test_fcp("First contentful paint fires due to background image in image-set.", load_image);
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-bg-image-two-steps.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-bg-image-two-steps.html
new file mode 100644
index 0000000000..89b161f859
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-bg-image-two-steps.html
@@ -0,0 +1,44 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP should fire for background image only when visible</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+    }
+
+    /* contentful and preFCP classes are defined in test_fcp script. */
+    #main.preFCP {
+        visibility: hidden;
+    }
+
+    #main.contentful,  #main.preFCP {
+        background-image: url(../resources/circles.png);
+    }
+
+    #main.contentful {
+        visibility: visible;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main"></div>
+<script>
+    // Load the image into memory first to make sure it's decoded.
+    function load_image() {
+      const img = document.createElement("img");
+      img.src = "../resources/circles.png";
+
+      return new Promise(resolve => {
+        img.onload = async () => resolve();
+      });
+    }
+
+    test_fcp("First contentful paint fires for background image only when visible.", load_image);
+</script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-canvas-context.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-canvas-context.html
new file mode 100644
index 0000000000..726e4516ee
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-canvas-context.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP when canvas context is created</title>
+</head>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<canvas id="canvas" width="50" height="50"></canvas>
+<script>
+  setup({"hide_test_state": true});
+  promise_test(async t => {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+    await new Promise(r => window.addEventListener('load', r));
+    await assertNoFirstContentfulPaint(t);
+    const canvas = document.getElementById('canvas');
+    const context = canvas.getContext('2d');
+    context.fillRect(0, 0, 100, 100);
+    await assertFirstContentfulPaint(t);
+  }, 'Canvas should count as contentful when context is created');
+</script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-image.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-image.html
new file mode 100644
index 0000000000..e407f68708
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-image.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html class="hide">
+<head>
+<title>Performance Paint Timing Test: Image FCP due to the documentElement's opacity</title>
+<style>
+    html {
+      will-change: opacity;
+    }
+    .hide {
+        opacity: 0;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main"></div>
+<script>
+// Load the image, add it to the DOM and make sure it's decoded.
+const load_image = () => {
+  const img = document.createElement("img");
+  img.src = "../resources/circles.png";
+  document.body.appendChild(img);
+  return img.decode();
+};
+
+const change_opacity = () => {
+  document.documentElement.className = "";
+}
+
+promise_test(async t => {
+  assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+  await load_image();
+  await assertNoFirstContentfulPaint(t);
+  change_opacity();
+  await waitForAnimationFrames(3);
+  const fcp_entries = performance.getEntriesByName('first-contentful-paint');
+  assert_equals(fcp_entries.length, 1, "Got an FCP entry");
+  const lcp_entries = await new Promise(resolve => {new PerformanceObserver((list) => resolve(list.getEntries())).observe({type: 'largest-contentful-paint', buffered: true})});
+  assert_equals(lcp_entries.length, 1, "Got an LCP entry");
+  // TODO: Rewrite this assertion after the FCP and LCP precision alignment CL is landed. Currently FCP start time has a higher precision than that of LCP. That means, even if the two are intrinsically the same, FCP.startTime will be larger as it has more fractional digits.
+  isLess = fcp_entries[0].startTime < lcp_entries[0].startTime;
+  isEqualToMicrosecond = Math.abs(fcp_entries[0].startTime - lcp_entries[0].startTime) < 0.001;
+  assert_true(isLess || isEqualToMicrosecond, "FCP should be smaller than FCP.");
+}, "Test that FCP after opacity change is not a larger value than LCP");
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-text.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-text.html
new file mode 100644
index 0000000000..12384d5585
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-text.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<html class="hide">
+<head>
+<title>Performance Paint Timing Test: Text FCP due to the documentElement's opacity</title>
+<style>
+    html {
+      will-change: opacity;
+    }
+    .hide {
+        opacity: 0;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">This is content that is extremely contentful.</div>
+<script>
+const change_opacity = () => {
+  document.documentElement.className = "";
+}
+
+promise_test(async t => {
+  assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+  await assertNoFirstContentfulPaint(t);
+  change_opacity();
+  await waitForAnimationFrames(3);
+  const fcp_entries = performance.getEntriesByName('first-contentful-paint');
+  assert_equals(fcp_entries.length, 1, "Got an FCP entry");
+  const lcp_entries = await new Promise(resolve => {new PerformanceObserver((list) => resolve(list.getEntries())).observe({type: 'largest-contentful-paint', buffered: true})});
+  assert_equals(lcp_entries.length, 1, "Got an LCP entry");
+  assert_less_than_equal(fcp_entries[0].startTime, lcp_entries[0].startTime, "LCP is not smaller than FCP");
+}, "Test that FCP after opacity change is not a larger value than LCP");
+</script>
+</body>
+</html>
+
+
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-ensure-update-the-rendering-step.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-ensure-update-the-rendering-step.html
new file mode 100644
index 0000000000..700707de33
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-ensure-update-the-rendering-step.html
@@ -0,0 +1,55 @@
+<!DOCTYPE html>
+<head>
+    <title>
+      Ensure the timing is marked during the `update the rendering` step.
+    </title>
+</head>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: 0px;
+        position: relative;
+        top: 0;
+        background-image: url(../resources/circles.png);
+        opacity: 0;
+    }
+
+    #main.contentful {
+        opacity: 0.1;
+    }
+</style>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="main"></div>
+<script>
+setup({"hide_test_state": true});
+async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+    let fired = false;
+    const main = document.getElementById('main');
+    let animationFrameStamps = [];
+    requestAnimationFrame(function frame(stamp) {
+        animationFrameStamps.unshift(stamp);
+        main.className = "contentful";
+        while (performance.now() - stamp <= 5) {
+          /* Busy-wait */
+        }
+        if(!fired)
+            requestAnimationFrame(frame);
+    });
+    new PerformanceObserver(t.step_func(list=>{
+        for (let entry of list.getEntries()) {
+            if (entry.name == "first-contentful-paint") {
+                fired = true;
+                assert_any(assert_approx_equals, entry.startTime, animationFrameStamps, 1, "One of the past requestAnimationFrame should have the same timestamp as paint entry");
+                t.done();
+            }
+        }
+    })).observe({type: "paint"});
+}, 'The first-contentful-paint timestamp should be same as the last RAF');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-gradient.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-gradient.html
new file mode 100644
index 0000000000..c1e147472f
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-gradient.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP should not fire with gradient-only backgrounds</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        background-image: linear-gradient(to bottom, orange, blue);
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main"></div>
+<script>
+  setup({"hide_test_state": true});
+  promise_test(async t => {
+      assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+      await new Promise(r => window.addEventListener('load', r));
+      await assertNoFirstContentfulPaint(t);
+  },  'Gradients should not count as contentful');
+</script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-iframe.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-iframe.html
new file mode 100644
index 0000000000..674bcd9121
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-iframe.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<head>
+    <title>
+        Performance Paint Timing Test: Not only the top level document, paints
+        in the iframe should also generate the entry
+    </title>
+</head>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+setup({"hide_test_state": true});
+async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+    window.addEventListener('message', t.step_func(e => {
+        if (e.data.entryType == "paint" && e.data.name == "first-contentful-paint") {
+            t.done();
+        }
+    }));
+    const iframe = document.createElement('iframe');
+    iframe.src = '../resources/subframe-painting.html';
+    document.body.appendChild(iframe);
+}, 'Parent frame ignores paint-timing events fired from child image rendering.');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-ignore-from-subframe.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-ignore-from-subframe.html
new file mode 100644
index 0000000000..7083a93db7
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-ignore-from-subframe.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<head>
+    <title>
+        Performance Paint Timing Test: Paints in the iframe should be reported in the iframe
+        and not in the top document
+    </title>
+</head>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+setup({"hide_test_state": true});
+promise_test(async t => {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+    const iframe = document.createElement('iframe');
+    iframe.src = '../resources/subframe-painting.html';
+    document.body.appendChild(iframe);
+    await new Promise(resolve => window.addEventListener('message', e => {
+        if (e.data.entryType == "paint" && e.data.name == "first-contentful-paint")
+            resolve()
+    }));
+    await assertNoFirstContentfulPaint(t);
+}, 'Parent frame should not fire own paint-timing events for subframes.');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-3d-rotate-descendant.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-3d-rotate-descendant.html
new file mode 100644
index 0000000000..76d459d0f4
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-3d-rotate-descendant.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to 3d revealing of descendants</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: 0px;
+        position: relative;
+        top: 0;
+        transform: rotateX(45deg);
+        transform-style: preserve-3d;
+    }
+
+    /*
+       This tests that given multiplication effect of 3d transforms on bounding rect,
+       An element counts as contentful/paintable only when its bounding rect is truly non-empty */
+    #child {
+        transform: rotateX(45deg);
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful {
+        transform: none;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+    <div id="child">Text</div>
+</div>
+<script>
+    test_fcp("First contentful paint fires due to its ancestor getting rotating into view.");
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-3d-rotate.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-3d-rotate.html
new file mode 100644
index 0000000000..0b7fc325c5
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-3d-rotate.html
@@ -0,0 +1,29 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to 3d rotation into view</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: 0px;
+        transform: rotateY(90deg);
+        position: relative;
+        top: 0;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful {
+        transform: none;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">Text</div>
+<script>
+    test_fcp("First contentful paint fires due to 3d rotation into view.")
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-scale-transition.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-scale-transition.html
new file mode 100644
index 0000000000..c0c0af0cdb
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-scale-transition.html
@@ -0,0 +1,30 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP in transition</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: 0px;
+        transform: scale(0);
+        transition: transform 1s;
+        position: relative;
+        top: 0;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful {
+        transform: scale(1);
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">TEXT</div>
+<script>
+    test_fcp("First contentful paint fires when revealed during transition.");
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-scale.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-scale.html
new file mode 100644
index 0000000000..4d3a060e85
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-scale.html
@@ -0,0 +1,40 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to scale change</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: 0px;
+        transform: scale(0);
+        position: relative;
+        top: 0;
+        background-image: url(../resources/circles.png);
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful {
+        transform: none;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main"></div>
+<script>
+    // Load the image into memory first to make sure it's decoded.
+    function load_image() {
+      const img = document.createElement("img");
+      img.src = "../resources/circles.png";
+
+      return new Promise(resolve => {
+        img.onload = async () => resolve();
+      });
+    }
+
+    test_fcp("First contentful paint fires due to scale becoming positive.", load_image)
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-text.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-text.html
new file mode 100644
index 0000000000..e1b38712a6
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-invisible-text.html
@@ -0,0 +1,30 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP should still fire for invisible text</title>
+<style>
+    #main {
+        position: relative;
+        width: 100px;
+        height: 100px;
+        visibility: hidden;
+        color: rgba(0, 0, 0, 0);
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful {
+        visibility: visible;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+    INVISIBLE
+</div>
+<script>
+    test_fcp("First contentful paint fires due to pseudo-element becoming visible.")
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-opacity-descendant.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-opacity-descendant.html
new file mode 100644
index 0000000000..8ada49b767
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-opacity-descendant.html
@@ -0,0 +1,46 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to ancestor opacity</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: 0px;
+        position: relative;
+        top: 0;
+    }
+
+    #child {
+        opacity: 0;
+    }
+
+    /* contentful and intermediate classes are defined in test_fcp script. */
+    #main.contentful #child {
+        opacity: 1;
+    }
+
+    #main.intermediate #child {
+        opacity: 1;
+    }
+
+    #main.intermediate {
+        opacity: 0;
+    }
+
+    #main.contentful {
+        opacity: 0.5;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+    <div id="child">Text</div>
+</div>
+<script>
+    test_fcp("First contentful paint fires due to its ancestor getting positive opacity.");
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-opacity.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-opacity.html
new file mode 100644
index 0000000000..3c6912c4e6
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-opacity.html
@@ -0,0 +1,40 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to opacity</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: 0px;
+        position: relative;
+        top: 0;
+        background-image: url(../resources/circles.png);
+        opacity: 0;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful {
+        opacity: 0.1;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main"></div>
+<script>
+    // Load the image into memory first to make sure it's decoded.
+    function load_image() {
+      const img = document.createElement("img");
+      img.src = "../resources/circles.png";
+
+      return new Promise(resolve => {
+        img.onload = async () => resolve();
+      });
+    }
+
+    test_fcp("First contentful paint fires due to opacity-revealed element.", load_image);
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-out-of-bounds-translate.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-out-of-bounds-translate.html
new file mode 100644
index 0000000000..ee7975eec4
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-out-of-bounds-translate.html
@@ -0,0 +1,30 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to transform-based intersection with document</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: 0px;
+        transform: translate(-1000px);
+        position: relative;
+        top: 0;
+        background-image: url(../resources/circles.png);
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful {
+        transform: none;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main"></div>
+<script>
+    test_fcp("First contentful paint fires due to transform-based intersection with document.")
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-out-of-bounds.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-out-of-bounds.html
new file mode 100644
index 0000000000..91556e50e0
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-out-of-bounds.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to intersection with document</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: -1000px;
+        position: relative;
+        top: 0;
+        background-image: url(../resources/circles.png);
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful {
+        left: 0px;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main"></div>
+<script>
+    // Load the image into memory first to make sure it's decoded.
+    function load_image() {
+      const img = document.createElement("img");
+      img.src = "../resources/circles.png";
+
+      return new Promise(resolve => {
+        img.onload = async () => resolve();
+      });
+    }
+
+    test_fcp("First contentful paint fires due to intersection with document.", load_image)
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-display.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-display.html
new file mode 100644
index 0000000000..50fd626e89
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-display.html
@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to pseudo-element text</title>
+<style>
+    #main {
+        position: relative;
+        width: 100px;
+        height: 100px;
+    }
+
+    #main:after {
+        content: "TEXT";
+        display: none;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful:after {
+        display: block;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+</div>
+<script>
+    test_fcp("First contentful paint fires due to pseudo-element text.")
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-image.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-image.html
new file mode 100644
index 0000000000..d67ae21cd9
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-image.html
@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to pseudo-element image</title>
+<style>
+    #main {
+        position: relative;
+        width: 100px;
+        height: 100px;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful:after {
+        content: url(../resources/circles.png);
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+</div>
+<script>
+    // Load the image into memory first to make sure it's decoded.
+    function load_image() {
+      const img = document.createElement("img");
+      img.src = "../resources/circles.png";
+
+      return new Promise(resolve => {
+        img.onload = async () => resolve();
+      });
+    }
+
+    test_fcp("First contentful paint fires due to pseudo-element image.", load_image)
+</script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-opacity.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-opacity.html
new file mode 100644
index 0000000000..b209864d5d
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-opacity.html
@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to pseudo-element getting positive opacity</title>
+<style>
+    #main {
+        position: relative;
+        width: 100px;
+        height: 100px;
+    }
+
+    #main:after {
+        content: "TEXT";
+        opacity: 0;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful:after {
+        opacity: 0.5;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+</div>
+<script>
+    test_fcp("First contentful paint fires due to pseudo-element getting positive opacity.")
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-text.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-text.html
new file mode 100644
index 0000000000..ea2105e453
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-text.html
@@ -0,0 +1,28 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to pseudo-element text</title>
+<style>
+    #main {
+        position: relative;
+        width: 100px;
+        height: 100px;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful:after {
+        content: "TEXT"
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+</div>
+<script>
+    test_fcp("First contentful paint fires due to pseudo-element text.")
+</script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-visibility.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-visibility.html
new file mode 100644
index 0000000000..c903c47218
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-pseudo-element-visibility.html
@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to pseudo-element becoming visible</title>
+<style>
+    #main {
+        position: relative;
+        width: 100px;
+        height: 100px;
+    }
+
+    #main:after {
+        content: "TEXT";
+        visibility: hidden;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful:after {
+        visibility: visible;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+</div>
+<script>
+    test_fcp("First contentful paint fires due to pseudo-element becoming visible.")
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-svg.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-svg.html
new file mode 100644
index 0000000000..bcd2372cfc
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-svg.html
@@ -0,0 +1,40 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP with SVG</title>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: 0px;
+        position: relative;
+    }
+
+    #circle {
+      display: none;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful #circle {
+        display: block;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+  <svg viewBox="0 0 10 10" xmlns="http://www.w3.org/2000/svg"
+     xmlns:xlink="http://www.w3.org/1999/xlink">
+    <defs>
+      <circle id="myCircle" cx="5" cy="5" r="4" stroke="blue"/>
+    </defs>
+    <use id="circle" href="#myCircle" fill="green" />
+  </svg>
+</div>
+<script>
+    test_fcp("First contentful paint fires when SVG becomes contentful.")
+</script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-text-input.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-text-input.html
new file mode 100644
index 0000000000..e50449abbe
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-text-input.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due for non-empty text input</title>
+</head>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<input id="input" type="text" />
+<script>
+  setup({"hide_test_state": true});
+  promise_test(async t => {
+      assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+      await new Promise(r => window.addEventListener('load', r));
+      await assertNoFirstContentfulPaint(t);
+      const input = document.getElementById('input');
+      input.setAttribute('value', '  ');
+      await assertNoFirstContentfulPaint(t);
+      input.setAttribute('value', 'value');
+      await assertFirstContentfulPaint(t);
+  }, 'Text input should become contentful when its value is non-empty');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-typographic-pseudo.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-typographic-pseudo.html
new file mode 100644
index 0000000000..5ec62b7d59
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-typographic-pseudo.html
@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP should not fire when all text is hidden due to typographic pseudo-elements</title>
+<style>
+    #main {
+        position: relative;
+        width: 100px;
+        height: 100px;
+    }
+
+    #main *::first-letter {
+        opacity: 0;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful *::first-letter {
+        opacity: 1;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+    <div>A</div>
+</div>
+<script>
+    test_fcp("First contentful paint fires only when some of the text is visible, considering ::first-letter.")
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-frame.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-frame.html
new file mode 100644
index 0000000000..c54648f001
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-frame.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to loaded video frame</title>
+</head>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/media.js"></script>
+<video id="video" autoplay></video>
+<script>
+  setup({"hide_test_state": true});
+  promise_test(async t => {
+      assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+      await new Promise(r => window.addEventListener('load', r));
+      await assertNoFirstContentfulPaint(t);
+      // Set actual video content to trigger FCP.
+      const video = document.getElementById('video');
+      video.src = getVideoURI('/media/test');
+      await new Promise(resolve => {
+        video.oncanplay = resolve;
+      });
+      await assertFirstContentfulPaint(t);
+  }, 'Video should become contentful when first frame is loaded');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-poster.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-poster.html
new file mode 100644
index 0000000000..e7eeee3f12
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-poster.html
@@ -0,0 +1,28 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to loaded video poster</title>
+</head>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<video id="video" width="50" height="50"></video>
+<script>
+  setup({"hide_test_state": true});
+  promise_test(async t => {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+    await new Promise(r => window.addEventListener('load', r));
+    await assertNoFirstContentfulPaint(t);
+    const video = document.getElementById('video');
+    const src = '../resources/circles.png';
+    const image = new Image();
+    image.src = src;
+    video.setAttribute('poster', src);
+    await new Promise(resolve => {
+        image.onload = async () => resolve();
+    })
+    await assertFirstContentfulPaint(t);
+  }, 'Video should become contentful when poster is loaded');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-whitespace.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-whitespace.html
new file mode 100644
index 0000000000..71c72b018a
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-whitespace.html
@@ -0,0 +1,45 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: Whitespace should not count as contentful</title>
+<style>
+    #main {
+        position: relative;
+        width: 100px;
+        height: 100px;
+        background-image: url(../resources/circles.png);
+        background-size: 0 0;
+    }
+
+    #text {
+        display: none;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful #text{
+        display: block;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+    <div id="whitespace">   </div>
+    <div id="text">TEXT</div>
+</div>
+<script>
+    // Load the image into memory first to make sure it's decoded.
+    function load_image() {
+      const img = document.createElement("img");
+      img.src = "../resources/circles.png";
+
+      return new Promise(resolve => {
+        img.onload = async () => resolve();
+      });
+    }
+
+    test_fcp("Whitespace should not count as contentful.", load_image)
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-with-rtl.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-with-rtl.html
new file mode 100644
index 0000000000..5541fcbc72
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-with-rtl.html
@@ -0,0 +1,31 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to direction change</title>
+<style>
+  #text {
+    right: -100px;
+    position: absolute;
+  }
+
+  body {
+    direction: rtl;
+  }
+</style>
+</head>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="text">TEXT</div>
+<script>
+  setup({"hide_test_state": true});
+  promise_test(async t => {
+      assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+      await new Promise(r => window.addEventListener('load', r));
+      await assertNoFirstContentfulPaint(t);
+      document.body.style.direction = 'ltr'
+      await assertFirstContentfulPaint(t);
+  }, 'FCP should fire when coordinates are negative, if within document scrollable area');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/svg-in-iframe.html b/testing/web-platform/tests/paint-timing/fcp-only/svg-in-iframe.html
new file mode 100644
index 0000000000..230c166cb0
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/svg-in-iframe.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<title>Performance Paint Timing Test: SVG in iframe does not trigger FCP</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<iframe src="../resources/svg.html"></iframe>
+<script>
+  promise_test(async (t) => {
+    await new Promise(resolve => {
+      window.addEventListener("message", resolve);
+    });
+    return assertNoFirstContentfulPaint(t);
+  }, "SVG in an iframe does not trigger FCP in the main frame");
+</script>
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