chromium/src/third_party/blink/web_tests/external/wpt/css/css-scroll-snap/support/common.js

const KEY_CODE_MAP = {
  'ArrowLeft':  '\uE012',
  'ArrowUp':    '\uE013',
  'ArrowRight': '\uE014',
  'ArrowDown':  '\uE015',
  'PageUp':     '\uE00E',
  'PageDown':   '\uE00F',
  'End':        '\uE010',
  'Home':       '\uE011',
  'Space':      ' ',
};

// Send key event to the target element using test driver. Supports human
// friendly key names for common keyboard scroll operations e.g., arrow keys,
// page keys, etc.
async function keyPress(target, key) {
  let code = key;
  if (KEY_CODE_MAP.hasOwnProperty(key))
    code = KEY_CODE_MAP[key];

  // First move pointer on target and click to ensure it receives the key.
  let actions = new test_driver.Actions()
    .pointerMove(0, 0, {origin: target})
    .pointerDown()
    .pointerUp()
    .keyDown(code)
    .keyUp(code);

  return actions.send();
}

// Use rAF to wait for the value of the getter function passed to not change for
// at least 15 frames or timeout after 1 second.
//
// Example usage:
//    await waitForAnimationEnd(() => scroller.scrollTop);
function waitForAnimationEnd(getValue) {
  const TIMEOUT = 1000; // milliseconds
  const MAX_UNCHANGED_FRAMES = 15;

  const start_time = performance.now();
  let last_changed_frame = 0;
  let last_value = getValue();

  return new Promise((resolve, reject) => {
    function tick(frames, time) {
    // We requestAnimationFrame either for TIMEOUT milliseconds or until
    // MAX_UNCHANGED_FRAMES with no change have been observed.
      if (time - start_time > TIMEOUT ||
          frames - last_changed_frame >= MAX_UNCHANGED_FRAMES) {
        resolve();
      } else {
        current_value = getValue();
        if (last_value != current_value) {
          last_changed_frame = frames;
          last_value = current_value;
        }
        requestAnimationFrame(tick.bind(this, frames + 1));
      }
    }
    tick(0, start_time);
  });
}