amphtml: ${pageLoadTime} variable is not resolved after default pageview trigger

Short description of your issue:

${pageLoadTime} variable is not resolved after default pageview ("on": "visible") is triggered. It’s resolved later though.

Other similar variables (like ${contentLoadTime}) are resolved fine.

How do we reproduce the issue?

Check https://amp.mobify.net/lancome/http://www.lancome-usa.com/makeup

You’ll see that one of the requests to engagement-collector.mobify.net fails - it’s supposed to have ${pageLoadTime} defined.

Currently if I use this trigger:

"pageload": {
    "on": "timer",
    "timerSpec": {
        "interval": 5,
        "maxTimerLength": 600
    },
    "request": "pageload"
}

The first request has undefined ${pageLoadTime}, but only the first one. All consequent requests are fine. Originally I had this issue with another trigger (it’s deployed on the page mentioned above):

"pageload": {
    "on": "visible",
    "request": "pageload"
}

What browsers are affected?

Chrome 56

Which AMP version is affected?

1486153081489