observe-animated-image.tentative.html

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /largest-contentful-paint/animated/observe-animated-image.tentative.html - WPT Dashboard Interop Dashboard

<!DOCTYPE HTML>

<html>

<head>

  <meta charset=utf-8>

  <title>Largest Contentful Paint: observe image.</title>

  <script src="/resources/testharness.js"></script>

  <script src="/resources/testharnessreport.js"></script>

  <script src="../resources/largest-contentful-paint-helpers.js"></script>

</head>

<body>

  <script>

    promise_test(async () => {

      assert_implements(window.LargestContentfulPaint,

                        "LargestContentfulPaint is not implemented");

      const beforeLoad = performance.now();

      // Offsets inside `anim-gr.png`:

      //   IHDR: 8..33

      //   acTL: 33..53

      //   fcTL (1st frame): 53..91

      //   IDAT (1st frame): 91..254

      //   fcTL (2nd frame): 254..292

      //      fcTL payload starts at offset 262

      //   fdAT (2nd frame): 292..448

      //      fdAT payload starts at offset 304

//

      // The HTTP request below will stall for 2 seconds after all pixels of

      // the 1st frame are available, but before any 2nd frame pixels are

      // available.  The test will verify that LargestContentfulPaint fires

      // "immediately", without waiting for the rest of the bytes.

//

      // See https://crbug.com/393205780 why this offset (and not an earlier

      // one) is used in the test.

      const url = window.location.origin +

                  `/images/anim-gr.png?pipe=trickle(304:d${delay_pipe_value})`;

      const entry = await load_and_observe(url);

      const size = 100 * 50;  // `anim-gr.png` is 100 by 50.

      checkImage(entry, url, 'image_id', size, beforeLoad, ["animated"]);

    }, "Same origin animated image is observable and has a first frame.");

  </script>

</body>

</html>