content/test/data/back_forward_cache/sensor.html

<html>Pages with sensor script</html>
<script>
    let sensor;
    // Handles one event, pushing it to |values| and calling
    // |pendingResolve| if set.
    function handleEvent(event) {
        if (sensor.illuminance) {
            // For Ambient Sensor.
            values.push(sensor.illuminance);
        } else {
            values.push(sensor.x);
        }
        if (pendingResolve !== null) {
            pendingResolve('event');
            pendingResolve = null;
        }
    }
    // Collects values that have happened so far.
    var values = [];
    // If set, will be called by handleEvent.
    var pendingResolve = null;

    // Returns a promise that will resolve when the events array has at least
    // |eventCountMin| elements. Returns the number of elements.
    function waitForEventsPromise(eventCountMin) {
      if (values.length >= eventCountMin) {
        return Promise.resolve(values.length);
      }
      return new Promise(resolve => {
        pendingResolve = resolve;
      }).then(() => waitForEventsPromise(eventCountMin));
    }

    // Ensure that that |expected| matches all the values.
    function validateEvents(expected) {
      if (expected === null) {
        return "fail expected === null";
      }
      let count = 0;
      for (value of values) {
        count++;
        if (Math.abs(value - expected) > 0.01) {
          return `fail - ${count}/${values.length}: ` +
              `${expected} != ${value}`;
        }
      }
      return 'pass';
    }
</script>