User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:71.0) Gecko/20100101 Firefox/71.0

Steps to reproduce:

1. open Firefox for Android
2. open any extension page
3. debug that page from Desktop Firefox
4. execute following code:

(async () => {
  const timeoutPromise = delay => new Promise(resolve => setTimeout(resolve, delay));
  const tab = await browser.tabs.create({url: 'https://wiki.mozilla.org/', active: false});
  await timeoutPromise(1000);
  await browser.tabs.update(tab.id, {active: true});
  while ((await browser.tabs.query({active: true, lastFocusedWindow: true}).then(([tab]) => tab)).id !== tab.id) {
    console.warn('still not active');
    await timeoutPromise(1);
  }
})();

Actual results:

Depending on the device performance, the code can finish without any logs OR it will print still not active.
In the real life extension, actual activation took almost 300ms after browser.tabs.update finished.

Expected results:

browser.tabs.update should be resolved only AFTER the tab is really activated.

The priority flag is not set for this bug.
:jimm, could you have a look please?

For more information, please visit auto_nag documentation.

We fixed this in Bug 1616625.