Make OutputPageTest more independent from global state

This does not fix all problems (the "combined" test still fails
horribly on my machine for a reason I don't understand). However,
this patch fixes at least two of the problems:

Make the test independent from the wgResourceLoaderDebug setting.

Make the test independent from the wgLanguageCode setting.

Change-Id: I3aa52fed530d852b34b6058e29620749e11092a0
Merge "Make OutputPageTest more independent from global state"