1421662 - Consider removing BrowserTestUtils.addTab

Status: NEW

(Testing :: Mochitest, enhancement)

Description

[Tooru Fujisawa [:arai]]

BrowserTestUtils.addTab adds new tab and returns instantly before waiting for the load finishes.
each testcase needs to wait for load just after that,
otherwise the testcase runs in unstable state, that may result in intermittent failure (see 1421653).

BrowserTestUtils already provides BrowserTestUtils.openNewForegroundTab, that waits for load event by default,
so most callsite could be rewritten with it, or we can add similar function for background tab if really necessary.

also, other testcases that directly calls browser.addTab should also be rewritten with such function.